The Sejuani rework looks interesting; I love the current Sejuani and this could make her even better. The Trundle revamp looks neat as well.
For the Roleplay, if we haven't decided on a theme/setting, what if we made it based around 3-4 "Summoners" who were suddenly taken to Summoner's rift, either in the bodies of the champions they were playing, or as completely new champions. The RP would be the interactions that took place as/after this occurred?
Either way, if I do RP, I would love to play one of the current champions in the game, as opposed to making my own.