Champion Idea
Of course I'm going to suggest a playable Poro. Here are some ideas you could utilize with him.
1.) The poro fills the roll of support. 2.) You can sit on your adc to act as a shield. 3.) You can dash to the enemies to slow them and deal damage. 4.) Your ultimate turns you into/summons the Poro King. 5.) Your passive makes potions heal a set amount instantly.
I think it would be amazing to be able to play as a Poro. I doubt this will ever be a playable character but it sounds fun to me.
You could even change it up quite a bit compared to other champions. Make it less like a champion and more like a minion with abilities. When killed, the killer gets around 25 gold or so, but your damage is quite low (equal to that of a minion). Your main role would be supporting and it would be a purely utility based champ. The only item available to purchase would have to be wards. Sounds fun right? Thank you for any feedback you provide, good or bad.