If You Are Going To Get Autofilled,The Game Should Treat Your MMR As Being A Bit Lower
When I'm playing on a role that I don't have a lot of experience with, of course I'm going to play worse. I'm fine with that, as long as I don't unnecessarily cost myself and my teammates elo points.
Riot is already bringing Solo Que back and introducing a new seperate team ranked queue, which will already make games much more balanced because it removes the random factor of premades from the game. If the change described in the title will go through aswell, it would be even more balanced. And since you are changing ranked queues anyway, this change might aswell can go along with that.