Duo units and revival characters like Cell have shown some outside the box thinking. The next step would probably be characters with multiple transformations or two characters fighting at once. The effects you describe don’t seem impressive on paper but getting cards and Ki is all you really need to be good, it’s why transforming Goku Black is one of the best characters even among zenkai. I appreciate that they design characters in ways that they don’t all play the same even if it hurts their viability. such as Yellow Turles whose mediocre until he does his ultimate but it fits with his theme of having to eat the fruit; or Red SS Goku who gets a bonus from a dead Krillin teammate even though you’re not going to use a Krillin alongside him 99% of the time.> a unit that changes color with their main ability is just weird considering that color is the biggest weakness of all the units in the game
The element system is the bread and butter of every gacha, no matter how egregious it is in what is suppose to be a fighting game. I don’t think this will ever happen because it would be impossible to balance, being type neutral is already a powerful effect that few characters have and only for a short time. If some characters can just change colors permanently, then it invalidates the purpose of color countering. It would also give you less reason to summon if you have a character that can fill the roles of two colors on your team.