After a quick Google, I couldn't find an official forum for this game. It's possible that the developer doesn't want to deal with drama or grief, but hopefully some well thought-out feedback could be of use, and I'd like to see what else I haven't thought of. I hope updates are being planned.

* Only one save slot? Of course crude workarounds are doable, but meh. It's often nice to go back and see how far you've come in games like this.
* Exit to main menu --> resume game is essentially a free trip to the entrance, and therefore a free trip to any found teleporter. This isn't exactly OP as far as exploits go, but you might as well include a no-nonsense version as a feature up-front. Optionally, they could maybe even make exiting the game require a five-second uninterrupted channel if they really want to curb exploits and polish things up a bit.
* It's a bit early for me to know, but I'm really curious whether it's possible to genetically manipulate offspring later on. It's a real hassle to deal with classes you suck with sometimes. (answered below, but it would be fun to have more control than this in other game modes)
* As far as I can tell, there's no consequence for failing over and over in between good runs. A challenge mode where certain benchmarks must be met by certain years would make this Roguelike even more Roguelike. I'm pretty sure that I just plain suck, but beating the first boss in the year 2100 doesn't sound all that legit to me! X-D A game mode like this would prevent the player from feeding a character to the wolves every time a bad roll came up. Forcing the player to optimize each and every run would really tighten the gameplay experience.

Some or all of these features may already be present, but require unlocking. That would be sneaky. But off the top of my head, these are the features that would add a lot to the game IMO.

EDIT : * Journal entries pertaining to later areas should not be available in the n00b z0ne of the castle. As the game's only real storytelling device, it's really spoilery to be able to read ahead just because you keep dying in the first two regions well into the third millennium.
* (From Grombolar) Graphics settings and/or CPU optimization. This would probably be a lot more effort compared to return on investment, since the game seems to me and my mildly-outdated desktop like it would run smoothly on a relatively up-to-date gaming-enabled sort of hardware.
* (From Auntyjack) Please make the architect lockdown a toggle!
* (From a thread by Sarevok) Ability to play games in modes with "less plusses" (NG+ as a NG, NG++ as NG+ or NG, etc.)
* Current stun pattern: remain stunned and invincible until you land on the ground, and then the invincibility timer starts. This can be really annoying if you fall all the way down a pit and can't even change direction. Suggestion: Can this be capped at, say, .5 seconds at which time control is restored and the timer starts mid-air?
* Current children selection: You get to choose between 3 offspring. With a manor upgrade, you get one chance to "reroll" them. Suggestion: You just get one kid, but successive manor upgrades increase this number up to a maximum of five.
* Rogue mode: Bosses respawn every time, but you only get stat bonuses the first time you beat them. It would be a dramatically harder game, but probably beatable with a gamepad and some grinding, some tight play, and some intelligent choices about when to vamp and which statues to break when!

Having a low-end notebook (1.60GHz, 1 GB RAM & integrated video card), found it odd the game isn't optimized better - Full screen mode with maximum resolution & windowed mode with 640x480 BOTH have 7-8 FPS constantly when playing the demo version. When this is fixed, I'd certainly buy the game.

Any way to make the game run a bit faster? It's like being in bullet time the whole time...

Mine similarly can't really handle nearsighted or farsighted characters.

EDIT: I should add that they are a small team, so optimizing for ancient or non-gaming hardware just might not be worth it as a priority. Though it looks like a SNES title in a lot of respects, there are some special effects at times which would not have been possible back then.

One more for the list:

* Journal entries pertaining to later areas should not be available in the n00b z0ne of the castle. As the game's only real storytelling device, it's really spoilery to be able to read ahead just because you keep dying in the first two regions well into the third millennium.

It just feels a bit odd that be it 320x200 windowed mode & nothing moving on the screen, FPS stays the same the whole time, which is a shame. Am hoping they make a patch to "fix" this + a possibility to remove certain graphical options (such as rain, lightning, lighting etc). Until then I'll just have to wait until my laptop breaks down & buy a better one :P

Sadly I don't even know what those traits do precisely for some odd reason lol *sniff*

Anyway, the devs ought to add the features to get rid of extra eye candy if it'd sort out the lag problem... Iji, Spelunky, World of Goo, Gish among others work great for me.

All it does is introduce a fuzzy filter over the screen. Where it adds it depends on if you're nearsighted or farsighted. It's more annoying than anything else, as far as I've experienced, but it's possible to find an item called the Nerdy Glasses that removes the trait by giving you a pair of spectacles.

Still playing the demo version (SLOOOOOOWLY, mind you), yet to met such trait. On the plus side, having 8 FPS makes killing enemies easier, but jumping bit is bloody hard lol.

Gawddaymnit, was given a site which lets you play the game with low-end puters fluently (30 min trial), even farsighted -trait didn't lag... Sadly the billing bit currently only works in the US, Canada & UK... I'm going to cry myself to sleep.

How about when you lock down the castle, it stays locked (still with the gold penalty) for future generations until you unlock it again?
A few times I've had a good layout I wanted to keep exploring but rushed ahead without stopping by the Architect first... :(

That's a good one. I updated the OP. Thanks, I've been a victim of the same forgetfulness myself.

I finished the game a few hours ago and I think it would get a huge replay value (à la Spelunky) if there were a mod that could get rid of the manor and the leveling system (both for the hero and the monsters) so the gameplay would be skill-based only (with the help of runes and equipement only) with no gold farming. To do that efficiently, the equipment weight shouldn't exist anymore (or be adjusted to a certain a level) and the upper-classes (such as archmage, hokage and so on with "special move" button) should be unlocked from the start. That way the game would feel like a real old-school Castlevania (the 8/16 bit ones) with some tweaks to choose before each run.