Let's say some of us are right in assuming console/controller players will be at a disadvantage to PC players. The worst case scenario for a matchmaking system incorporating both PC and console players is that it balances itself out in a short time. If PC players do have an inherent advantage, the matchmaking system (after a bit of time to set default rankings) will show the majority of console players at low-middle MMR and more PC players in middle-high MMR. But I didn't mean that the matchmaking would be an issue (after a time you would get balanced matches despite of the platform as you said). What I wanted to point out is the ladder. If players can compete separately, I find that it's weird to then mix them in the same ladder. It would be like if you choose the nba champion without matches between conferences. In other words, if crossed play is supposed to be optional, you should also be able to choose your own platform ladder. And if ladder is mixed, I think that crossed play shouldn't be restricted to optional. (I guess that I'm pro "all or nothing" xD)

I also think it's pretty outrageous to think ALL console/controller players will be worthless to the competitive scene. There's a pro LoL player who uses a track-ball instead of a mouse, another high diamond/challenger LoL player who only uses a track-pad on his laptop, and a pro CS player with no limbs. To think there won't be a few console players in high MMR/the competitive scene would be fooling yourselves.

About esports, I think that it's a different enviroment. Most top players would probably end up using the same controller whichever they find more optimus, but if choose is free, the competition is fair. And arguments here like "I only like to play with consoles and I can't compete in Gigantic beacuse pc/mouse players are op" or "I haven't access to a controller or whichever" aren't valid in that enviroment because it's supposed to be a "proffesional scene".

Anyway, I agree that it's hard to know the best way as it's kind of a new thing.