Rather than new content, I'd personally like to see an extensive fix-up pass over old content. The #1 feature I'd like to see generalized to all scenes would be "genitalia selector" for all relevant scenes. I'm tired of people putting it in my butt when I have not one, not two, but THREE other holes over here for them to use. It's also frustrating that I can't have three of Sera's kids at once because she always goes for hole #1, and stuff like that.
Along similar lines, I'd also like to see micro-expansions of old scenes to include comments or acknowledgement of things like extra-sized parts, mini-sized parts, bizarre alien biology, and so on. There's already a lot of content in the game, but much of it is unsatisfying for heavily-modified characters. Frankly, I'd like to see more characters go "Uhh..." and hesitate or back out of a scene if it turns out that your Steele is grotesquely over-modded in a way that they're not prepared for or comfortable with.
Edit: It'd also be nice to see more acknowledgement of the character's race, height, weight (thickness), and tone in existing scenes. Very few scenes take those into account at all aside from the automatically-generated descriptive text ("sculpted backside", etc).
I'd also like to see a way, even if it requires digging into the Codex, of viewing characters' max penetration size. Simply being told "too big" and having to guess is a little tedious.
As far as new content, well, I'd like it if more bedicked NPCs -- particularly crewmembers -- could knock Steele up. Penny, Syri, Azra, Ardia, Amber, Kase, et cetera. Chaurmine, too. Urbolg? Honestly, I'd like it if every vaginal penetration scene could result in pregnancy, although I know some of them are less likely than others.
I'd also like to see more "business" content. The ability to buy and manage shops, or set up shops, or even just invest in businesses. Some other ways to passively earn credits, because boy, things start to get mighty expensive when you get to Dhaal!
Actually, a really fun idea for an alternate income source (that links into my fetishes, hee-hee) would be if you can authorize Steele Tech to use your kids in the nursery for tissue samples and whatnot. Encourages female players to have a wide variety of star-spawn.