New Kit Concept: Respec

So I was having this inner discussion about whether or not you could create a viable champ kit based around your ult being a respec. 1 pt at lvl 6, and the rest of the spells having additional tiers that, when maxed out, provide an additional effect. Something like reconfigurable "mini-ults." This could allow the champ to be extremely versatile, hard to predict, and fun to experiment with. Imagine your Yi gets fed early game and carries. If the other team is super tanky, he's not going to be much use late game. But what if you could rebuild him as a mage? I'm not great at figuring out the mechanics and balance of things like this, so could this actually work?