Still not got transformation ideas down yet....
If we're going with a Shantae sort of parallel, it would be an ideal transformation for Hypno-tan to turn into a Succubus, who can fly, and has the best seduction powers (Which makes fighting enemies easy). Of course, such a transformation would be *later* in the game where most of the gameplay is already said and done.
Other transformations could include a Naga transformation, which is more of the close combat fighter (Seducer?), reaching for enemies with her tail and breaking them down, also useful for entering smaller, more compact areas.
A belly dancer (Or some kind of dancer/musician) would be a consideration, being able to seduce enemies from afar, possibly controlling their movement, as well as being able to interact with music/dancer based objects and puzzles.
As for the game itself, I can and probably will help with programming, or just do it as a lead in GameMaker Studio, as that's what I'm most familiar with, and as long as you can animate it or give me an idea to make, I can do it. I *am* in the middle of another project, so either I would have to deviate time for this one, or wait until the first one is complete until I start on this one.