Co-op is big. Design all the missions with co-op in mind, much like the new Red Alert. In Sacrifice, many missions already pair you with an AI controlled mage so it is not a big leap.
Also, pvp multiplayer could become much more interesting if you allied yourself with a god and fought other mage's in duels or giant multi-mage battles to expand your god's land on a persistent map.
I think a lot of mmo (WoW especially) and of course RTS players would be drawn to this type of game and it would do extremely well. Here's hoping.

I would just be happy with new couple new gods and maps.. game is good as it is in my opinion but co-op would be great... ohh the possibilities :)

Warning: Huge wall of Text!! , below are the ramblings / dreams of a geek / game designer wanna be.
I would love to see a Sacrifice 2 being made sometime in the near future, the original sacrifice is/was a master piece and is still one of my favorite games.
Having said that I think that who ever decides to design / develop the sequel will need to make sure that they avoid the issues the original game suffered.
Sacrifice on its base level is simply great, having said that, as most of you may already know the game did not do well marketing wise, in my humble opinion I think that if there is ever to be a Sacrifice 2 then the game would need to be a bit more familiar to the general RPG / RTS player base.
I think that one of the reason Sacrifice did not do well in terms of sales was because the following:
1 - The game's learning curve was un-familiar/ too steep for your general RTS player base
2- The game's world (creatures, concept of God's, souls etc) was strange as well.
If these two design obstacles can be overcome by the designer then the game's chances of success will greatly improve, as we all know playing sacrifice is very fun, once you manage to get used to how everything works :)
As Cheeseloaf said, this is more of a dream so I here I am throwing my so called dreams and hopes for Sac2
1 - Units redesign:
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Re-design the some of units appearances so that they're more familiar to your casual gamer, for example the Charnel and Pyro's T1 melee units could be changed to look like a humanoid while retaining the same characterstics, another example would be giving Persephone's druids a staff to use as a weapon instead of looking like a king-fu happy gangster :)
The concept would apply to some of the more bizzare units, you dont want to radically change everything but instead make the units look like something a player can identify with
going back to the idea of re-designing some of the T1 melee units, what if Charnel's T1 melee looked more like Razael from Legacy of Kane, they would be holding a Scythe as a weapon (which would fit with their name) for those who are not familiar with Razael here is an image: http://web.gameguru.ru/wallpapers/wallpapers/soul_reaver_2/soul_reaver_2_large_5_1024.jpg
2- diversify the units abilities and provide an enhanced units interface:
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Sacrifice mainly works on the concept of Rock Paper Sicissors which does the job really well for the game IMHO, having said that it would be nice if some "flavour" was added to the game's units, for example if you take T1 ranged units, when engaged in melee the units still use their bows (rangers, Sylphs) , what if they could fight in melee instead? granted they wouldnt be doing the same amount of damage as a real melee unit but they would provide a sense of a more "realistic" (using the term here loosely)
The above was implemented to a degree in the original game, the Hellmouth can fight in both melee and range (although it does so randomly)
In addition the interface would need to have some enhancements, it was somewhat hard in the original game to get units within a group to use their abilities in combat since you were only able to activiate one ability at a time (the ability of the highest ranking unit in a group)
Perhaps adding some sort of an auto cast feature too?
3- Mod Support
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This is huge, Mod / Tech support can pretty much make or break a game, looking at some of the prime examples out there, Warcraft, Dawn of War, never winter nights, Elder scrolls, these games became a success because the developers / publishers were comitted to supporting the game and cultivating a thriving community, it is crucial to the success of any game IMHO.
Sacrifice came with Scapex which is an amazing tool, I have used it in the past to create single player campaigns with very engaging storylines and complex scripts (thats back in the day when I was a noob at desgining), having said that Scapex alone was not enough.
Without continued support from the devs and publisher it is hard for a community to stand on its own, in addition to fully unleash the creativity of the game's community more tools would have to given for them to further mod / enhance the game.
The above is just my 2c , I hope it didnt give you a headache when reading it and I hope it made sense, I really do hope that someone sees this and continues this discussion, a Game like Sacrifice should not be allowed to become forgotten for the simple fact that it was a brilliant piece of work.
Xeph

I agree with the above poster's 1st point; the units in Sacrifice could use a make-over. I've played through this game twice, only having discovered it on gog.com not long ago. During those playthroughs I sided with Charnel and James, and none of the units really stood out. If you ask me the color, shape or name of any of the units, you'll find me at a lack of words. More variation in color and shape (size, design etc.) would be nice; anything to easily spot and distinguish them on the battlefield (the sillhouette is important, as TF2 taught me).
Other than that, I really missed the lack of descriptions on some of the units/spells. I know this is blasphemy to some, but I really hate to RTFM, however well written and nicely designed it is. Except some small explanations of newly introduced units during the early missions, I didn't know what my spells did or how my units behaved (I looked them up in the manual as I advanced in missions, but even that doesn't inform you about the latest spells and units you receive). I get that some people find it interesting to figure out what they do by themselves, but not everyone does; me included. In the heat of battle, I'd like to know what that huge cow I just summoned did, without having to study its effect, which robs my attention from more dire matters.
Here are my wishes for Sacrifice 2:
- More unit variation in regards to color, shape and size. Make them distinguishable from another, even over great distances. This also holds true for wizards.
- More information about spells and units in-game, as mentioned above.
- More varied areas, with a greater amount of detail (the desolate and uninteresting areas in Sacrifice may be due to engine limitations, but I'll add this point anyways).
- More area-affecting spells. By that I mean terraforming spells like James' Hail of Rocks (or whatever it's called) and that thing where something bores a hole in the ground. Those spells are kewl. Also, weather-effecting spells could be more awesome visually. The tornado is powerful and all, but it looks rather silly just moving around with the area remaining unaffected (or maybe it does affect the area, and I'm just blind).
- Better variation in singleplayer missions. I'm guessing this is rather tricky with RTS games, since most singleplayer missions are really multiplayer battles in shoddy disguise. I liked Warcraft 3's approach to this, e.g. the missions where you only had a limited number of units whilst traversing through dungeons etc. Sure, Warcraft 3 also suffered from this flaw, but those that didn't are the ones I remember, it being a long time since I last played it.
- Better introduction. I really had no idéa what to do when I first started up the singleplayer campaign. Yes, yes, RTFM, but couldn't they have made a nice, little (or grandiose) introduction movie? Not Blizzard quality, neccessarily; pictures accompanied by voice-over / text and music would do (could be Sacrfice does have this, but in that case I've missed it). The retrospective narrative didn't work that well, IMO, with nothing to relate to from the beginning. I'd also like a better introduction of each god (don't you dare tell me to RTFM), as they didn't reveal much about themselves at the start.
- Story variability. Hey, what if I suddenly thought Marduk was a really cool guy and wanted to join forces with him? Then we could go on and battle against the other gods in a glorifying battle of (dare I say it?!) epic proportions, in order to end the world. This doesn't fit with the Eldred character, though, so maybe the wizard we control in Sacrifice 2: The Return of Charnel could be a blank slate, so that we may direct his/hers story on our own? It may even attract more fans of the RPG genre. Heck, that would even give us the chance to customize his/hers appearance! Oh, jolly good. HEY! WHY NOT BRING IT FURTHER?! You could give us the chance to customize the wizard's skills and abilities! Want to focus on stronger and more powerful summons? Put more points in Summon. Wanna blast away all resistance with the spell Bovine Invasion? Put more points in Spells. Maybe simplify it by choosing between any desired number of pre-made concepts. Either you focus on summons, spells or both equally (which means you won't get the strongest summons or the most powerful spells).
- That it is made. Please, developers of Sacrifice; band together and make a sequel! Of course, that's up to us costumers, so I' ve already started doing my job by spreading the Word of Charnel to my friends (Charnel ftw!).
Right. Time to play through it again. I'll go and hang out with Stratos this time.

hey, i just need new gods/minions/spells, more than 5 souls for some creatures, and different structures including anti-air turret and i'll be fine, LOL :P
But here of some ideas in full detail:
Anti-air turrets - No, not like warmonger bullets, (well..maybe) but they could shoot the level 1 attacking spell of the applicable God. i.e. they shoot things like wrath, lighting, fireball ect.
Obviously they would only shoot at air units :)
PYRO STUFFS
Pydroaulic Dynamo - Yes, it's already been made, but what if you could build them, HMMM???!! They could be just like in the single-player storyline, where they make volcanoes erupt in a random place on the map.
Pyro's Magnifryer - Yet again, this too has been made before, but nobody has ever actually made one! (These would be exactly the same as they were in the sacrifice campgain)
EDIT: ALL STRUCTURES WILL BE MADE ON MANALITHS, IN CASE YOU WERE WONDERING
God Campgain
Aswell as the original singleplayer storyline involving you playing as a wizard and choosing which Gods to fight for, you could actually play as a God, except as a Commander. What i mean is, you choose a God and then you must defend and take over the different islands until you get full domination or kill the other Gods. However, if an enemy wizard invades your Gods home island, then it's game over :'( . But first..let me explain it. When you start you can choose what to do, such as attack an island of a rival God. (sometimes a God will ask you to be an ally) You choose wizards of your God to send (or maybe you could pay a wizard without a god, such as the Hachimen) into battle. Also, if you choose one Wizard to do that, another wizard could help defend one of your islands. Of course, before you command a wiazrd, you have to supply them with creatures. You get creatures daily (a day on the game) by recruiting them. The more recruiters you have, the more creatures and stronger creatures you recruit! I have alot more ideas of this, but i forgot. Oh well. ¬_¬