I think the biggest mechanical change I want to see is that tease-focused characters shouldn't be gimped in any encounters. Whether with a tool that can either turn their desirability into damage or a lack of combat-only encounters I don't really mind. I just felt like having a whole separate progression alongside combat skills that was effectively worthless compared to them was a detriment to both CoC and TiTS.
Content-wise I've been really happy with the civilized insectoids (Ant princess in CoC, Bothrioc and Myr in TiTS). Wasn't a huge fan of Zil or the Spiders/Driders in CoC because I feel like these "savage" races end up really shallow.
I did wish there were more depth to the Venus Pitchers in TiTS, because their scenes were great but there were only like 3 of them. (also the completely unfinished seeds that I'm totally not salty about) I'm not a big fan of the hypnotism whether or not it's consensual. I'd much rather be able to be fully in control of what I do, even if the result for the creature I'm encountering is pretty much the same. I realize that's a personal preference thing though so whatever.
I think its worth mentioning that I was really disappointed when races crop up that basically only act to drop transformatives and XP, with no depth to the race itself. A lot of races have suffered from this and I'm sure that while some people are fine with it, I'd MUCH rather see fewer overall races but with much more compelling stories and depth to them. Transformatives that people commonly want could be sold, or could be included in the starting races options.
One thing I've wanted for is the option to lock down my character's transformations once they get to a spot I like. It always felt weird to me that some transformations were irreversible (Galomax) while others could be altered against your will. Sure this "lockdown" should be rare or expensive but I think its worth including. (in fantasy this is often called "immutable form" btw)
Finally I'll just drop the subjects that I'd put on a wishlist.
- Tentacles more similar to venus pitchers than tentacle monsters.
- A way to end pregnancies instantly (effectively abortions but really it could be magic or something).
- Actual Consequences for losing fights, and I'm not talking Bad Ends. I mean things happen to the world or your character that you can not change without savescumming, but that don't just end the game.
I guess lastly, don't half-ass any of the content. If you're putting something in the game that isn't gonna make the game better, maybe you should look at whether it goes in at all. I know donors can request things, but maybe y'all should take a look at the request before accepting the donation to make sure you want it in the game at least half as much as the donor does. Some of my favorite parts of these games feel unfinished (see venus pitcher, lake slimes, tease mechanics, harpies, Queen of the Lake on Myrellion). I want to see a game the team is proud of more than anything else.