Zac & Teleport interaction
I don't think they should let an ally teleport to Zac's passive, making him invulnerable. He technically should count as a champion. The teleport gives him an unprescendented amount of invulnerability - far more than any other source, including zhonya's, kayle ult, and zil ult (while reviving).
It makes an already strong champion that much more oppressive, and doesn't even stop the timer on his passive so it all but guarantees that he'll revive without any counterplay at all.