Given the various technical and graphical glitches we've already seen, you might be surprised. Granted, Wonderwing and Yggdrasil aren't terribly boundary-pushing by themselves (Wonderwing might have been a balancing concern when they were drafting it), but I'm sure developers thought the same thing about Blanka's electric charge or many other oversights over the years. Ikki got changed because of programming issues (my 2D unique character interaction animations combined with the 3D treasure chest). For all we know, one of Pokémon Trainer's Pokémon standing on a section of breakaway bridge as the cannonball hits causes the game to freeze because both Risky/Tinkertub and the Pokémon Trainer are background objects. Who knows. Look at Terry's Buster Wolf vs. Popo.
The invincibility on the transformations that I posit (in the event that they don't want it to return Shantae to default state on interrupt ala Wonderwing) is both a technical and balancing challenge. A worthwhile challenge to explore, in my book. Same for the breakaway platforms.