Mods would be great, agreed. But I'm not code savvy, or modeler-y, enough to even begin trying. I can read code decently well, but actually writing it is a no go, except for super simple things. I'm even worse at modeling/art.
Adding other forms of vore wouldn't be too tough, visually at least, as you'd just need to add stretching the mouth, throat, and chest, along with the the belly (Or add a butt/puss stretch>belly) animations. I'm sure distorting the models wouldn't be particularly difficult, though actually setting up the animation and coding it to work properly would more difficult/time consuming.
The hardest part (not to say that any of it would be easy, per say.), I assume, would be actually changing the game to swap the CV for whatever type you wanted. After that, adding new preds would be almost as simple as adding copies of the Dragon's AI to different models and telling it which vore to you. After that, you'd have to add in the release, so scat for AV/Oral and a blast of liquids for UB.
I don't like scat, so as much as I like Oral more, I'd be a bit leery of actually using it, as you'd have to add scat for the disposal part, as well as some way to move the remains for the 'hide the victim' objectives. Diapers, probably. Just thinking about it icks me. UB disposal...I'm not sure how you'd do that one...Most UB with melting into liquids just has it spray everywhere, which, while it would be fun visually, again you need to have a container of some sort to 'hide' on certain maps, and unlike CV we can't use condoms, not without it being immersion breaking...not that there's a ton of immersion in this game. Having to think about this sort of thing might be one of the reasons the game is CV only. Easy disposal option with condoms, not as gross as a bunch of poop being dumped all over, etc.
As for 'stealing' prey? That'd be interesting. You'd have to add movement to clones of the sex-able 'stations' throughout the maps, allowing them to roam, then add code for forcing you into sex. It'd be pretty easy to explain, lore-wise, as the world the game takes place in is obviously quite repressed, sexually, so they are people that have finally run out of patience and don't care about the consequences anymore. It'd be a neat obstacle in maps, as well, since having sex and being caught by a guard would be pretty bad. Also, you'd probably need to make the guards hostile to them as well, at least a little, since they're breaking the 'no sex' rules.
Again, personally, I'd have no idea how to do it, so if it happens it won't be me. xD Definitely would love it though. If anyone wants to try, all I can say is "good luck".