What if we had a champ who could grant stealth to an ally?

Would this be a fun mechanic in your opinion or would it be too hard to balance? Obviously it would be strong, but it's not like we have a lack of broken, game changing abilities in LOL. I've been thinking about an idea for a new champ and I keep tossing around ideas for a chemist champ whose potions grant useful effects to allies (think of it like Singed except he can give potions to allies as well). The stealth would be his ultimate, since it would be WAY too strong early game. As for how it works think of it like an invisibility potion in games. You drink the potion and then you gain invisibility for 'x' number of seconds. What I'm not sure about is how his abilities should work. I'm thinking they could work one of 2 ways. He either picks an ally and gives them a potion (and they get to choose when to use it), or the potion is used the instant he gives it to them. Anyways what do you think?