Mind if i give you some ideas? This game is really hot and i'd LOVE to have a part in helping.
Viewing post in Witch's Table: TF Roulette comments
First idea: sandbox mode. Basically, just see how far the transformations will go with no risk of losing
Second: name based secret characters. (Examples: toriel from undertale, hornet from hollow night, toy chica from fnaf 2 because I know the freaks that love the overly lewd pizzeria chicken, etc)
Futa mode: basically just gives everyone a cock at the start (different cocks for different secret characters if you're willing to put this much depth into the stuff)
Donut potion and lip expansion potion: puffy anus fetish and hyper lips fetish respectively
Multiboob potion: literally in the name (an extra rack added to the character, 3-4 pairs maximum)
Lipples potion: lip nipples
That's all I can think of at the moment.
The sandbox mode is already available (endless checkbox in options). Also check out the modding documentation in the 1.0 download. At least some of the tfs you mentioned (multiboob would be possible but a pain, the rest would be a TF tagged potion, see the template) can be implemented using it. I plan to focus on rewriting a lot of the more clumsy lines and polishing the game before adding additional middling quality content myself, and secret characters would be a systemic rewrite of how descriptions currently work (though reworking it to add the ability to mod characters/descriptions is planned for a month or two down the line, v2.0).