Champion idea
Well first of all, I don't know if someone has ever come up with the same idea as me on the forum, so if it has been said before, i'm sorry.
What would you think about another transform champion, that would be a mage girl with somehow long range attack and CC, that could transform into a short range boy who would do physical damage?
I know it seems similar to Jayce but with a different gameplay, the girl would be more about stunning ennemies from afar dealing moderate damage, and the boy could be more tanky with the stats that change at the same time.
Maybe a little messy but it would be a new kind of gameplay I think for a champion! :)
transforming into 
: stun enemy with E, do some burst with spells, switch to melee and clean up.