What happens when you get filled next season?

Seeing as there are changes to how you get ranked depending on what role you queue for I have a couple of questions and suggestions regarding getting filled. If I queue up for a game with mid primary and I get filled support, will that game go to my mid rank or my support rank? Will I get placed against people based off my mid rank or my support rank? I think riot should just scrap the idea of separate ranks entirely because it will effect higher elo players a lot. People in challenger get filled all the time because most of them play a popular role. What's going to happen to them when they get filled? Am I going to have to worry about challenger smurfs in my games? How will you prevent this from happening? Adding ranks dependent on role is going to increase the amount of smurfs as well since people can just queue for a different role and be matched with lower elo people immediately. Also how will queueing with other people work? Will it be based off of what role has the highest rank or what rank I'm queueing for? I really hope riot rethinks this idea or at least gives information in general and on how they plan to counter people smurfing by playing a role that they purposely keep at low elo.

TLDR: If I get filled which role's rank (The one I queued for or the one I'm filled as) dictates who I'm going to be matched against and what rank will be effected? What about smurfing?