Would a hybrid concept hero that shifts it's AD to AP and visa versa be too complex for League? It could create an interesting champion... but it'd have to be noted that like 1.4 AP = 1 AD as far as value(not sure of actual value ratio).
I'm not talking an absolute clone, just that one trait. Possibly a form shifting ulti much like nidalee, jayce, and elise...
The rest of the kit would be up for grabs to experiment with.
(to avoid downvotes for mentioning DOTA... I'm not saying morphling is a great hero design and should be in League, or that DOTA is better/worse, or that complexity is bad/good. I just understand(and actually like) that League tends to be simpler and avoid excessive complexity)
Kayle used to have a passive that gave bonus AD based on AP and visa versa, which was an awesome passive that essentially allowed her to build and offensive route effectively. That type of passive could even be implemented here(at a lower ratio probably though).
EDIT: Mods suck and moved this too off-topic. Dunno why.