I don’t think keeping ult change would work. Sounds like it would be a bit frustrating and hard to predict.
Ult charge is a real reason why people don’t switch though. But I think just making ults less impactful is a better option.
You should he a hero you are good at that wins a game, not the hero’s ult. Like Zayra, you could be really bad but her ult is actually pretty easy to huge and is massively impactful.