Sure thing.

Also, a quick test shows that Dread Reapers are helpless against Wraiths (Invoke Death doesn't work on wraiths), but doom priests can dominate a wraith. So Undead also use their priest unit to deal with wraiths.

To my eye, the Charlatan has a wide range of abilities, but most of them aren't very good. To that end, I'd give it one of Wall Climbing, True Seeing, or increased Vision (probably Vision 1/2/3). Don't lower the cost if adding any of these abilities, though.
-Wall Climbing puts it in a similar category with Fairies, Rogues, and Assassins. It can sneak around solo and snipe undefended structures.
-True Seeing makes that ability available for Humans. A single Charlatan in every Air Galley might not be a surprise with True Seeing, but don't also give them Vision 1-4 or you make Air Galley combos even more disgusting since nothing could hide from them. Make the Air Galleys work for their kills at least a little bit.
-Extra Vision range makes the Charlatan a better scout, keeping an eye on an important enemy target or scouting ahead of a Human controlled army.

I'd probably lean toward giving the Charlatan Vision or a minor cost reduction. The Humans as a race shouldn't have an answer for everything in addition to being a Neutral aligned race.

I don't think I'd change Musketeers any. They fill a similar role to siege machines. They have infantry speed (unlike siege), they have only one shot (like catapults), but they are more accurate than catapults and have higher damage than ballistas. They don't damage walls, but they are significantly cheaper than the T2 siege.
You could make "Fire Musket" shoot twice per action, but you'd need to jack up their cost to at least 80 gold to account for how they would be super ballistas.

Either way, neither of these units really need a cost reduction. I could see maybe reducing the Charlatan cost down to around 50 gold instead of giving it a new ability, but keep in mind what other units cost when adjusting prices.

Good point about the Vision+True Seeing combination, which I hadn't properly considered.

I think it's easy to overrate cost changes for tier3/tier4 troops, since I don't think it's fallacious to factor in a few turns of maintenance to get the 'real' cost, so even a 1 gold troop would have city upgrade cost, maintenance, and opportunity cost.

Abilities can't be modified, or rather the only person that knew how, Warlock of the eponymous mod, went AWOL about 15 years ago(?)

I think you greatly overrate the musketeer, which I see being mentioned as very weak a fair few times on the old site. Correct me if I'm wrong, but Catapults are never worth using in PBEM, because their strength was taking down walls with impunity in tactical combat; so the musketeer being better than a catapult for killing troops isn't saying that much.

Musketeer's only advantage over a ballista is being faster than it, and that advantage is only relevant if you don't have Air Galleys (which sometimes you don't to be fair, if say it's an Elf player with a 3hex human town). They do a little less than 70% of the damage because the ballista shoots twice, 71.4% of the HP, take more infrastructure and time to train. Even the 27 cost advantage gets eroded upfront by city upgrade costs and over time by +2 maintenance. I think the musketeer would be an equal to the ballista (better pre-Air Galley, worse after) if it was a tier2 unit. But it's tier 3.

I haven't really considered that aspect too much. I'd assume most pushes to T3 probably have a specific unit in mind, and for humans that is almost certainly the Cavalier since it is a tanky bruiser on cavalry legs. That doesn't leave much space for the other two Human T3 to occupy.

For me, the Highman Avenger has a similar problem. It has a nice stack of abilities, but it is competing against the Titan and the Valkyrie for attention. If I want a bruiser, I'm taking the Titan. If I want a mobile scout + sniper, I'm taking the Valkyrie.

I don't think I'm overrating the musketeer (and I don't think they're good units), I'm just saying its current cost sounds about right for its abilities when compared to what similar units cost and can do.

I suspect catapults aren't generally worth using because they are slow, they only get one shot per round, their shot isn't very accurate, and they are slow. Their range does let them shoot in the first round of combat, though. I'm not a big fan of siege equipment in general because it is so slow.

The Musketeer suffers from the randomness present in combat and the fact they are competing with Cavaliers and Archers for attention. If a Musketeer had two shots then it would actually be pretty fearsome, but only one shot (even at long range) leaves it too much at the mercy of the RNG. It could murder or get murdered, and there isn't a way to know in advance which one will happen. Cavaliers are much more reliable bruisers, while archers are much more reliable (if weaker) ranged units.

Since you can't edit abilities, I suppose the extra points of Marksmanship would be the way to go, starting with M2 and reaching M4 with medals. Higher attack means a better chance of hitting, which gives its high damage a chance to work. The flavor behind it (a dude with a gun) means you probably don't want to give it too much in the way of defensive values; I'd probably up the cost some if you give MM and extra survivability since it gets to shoot in the first round of auto-combat.

done

The day of the Dead

I don't see any Air Galleys and this is not good.
I am starting to kill my own units that are not useful

Humans, Day 64

Sorry about the restart, I realised I had my mod active when I first loaded it, which would have messed with things a bit.

Today, my 8 attack, 10 def hero died to a troll.

Day 64 of the Dead

Got some bonus gold for tomorrow

Humans, Day 65

We have caught the last Frostling forces.

(also my game crashed, sorry)

TS

Thanks for the game, everyone!

Day 65 of the Dead!

Will this be the last day of our undead conquest?

You are welcome, jyri. We should play again

Hope we play some more! (I won't use Air galley ballista again)

TS

Southern, please don't give up on Air Galleys. Without Air Galleys
you will be crushed very easily and this will be unfair.
We just need to learn our lesson that humans need to be attacked
before they have researched Air Galleys. That's all

Humans, 67

Air galleys are parking on the mountains above the undead cities.
oof :)

Dead 67

The machine army takes a key position. Call me John Connor. Dead John Connor