What About Making The Support Role Lose Less LP For Losses?
Basically, few players want to Support, why not give some more incentive?
Supports tend to have less impact in terms of carry potential (Mind you-- this is a generic statement, it doesn't cover the fringe cases like Lux or Brand Support who deal a lot of damage). The role is less exciting as you don't get to farm, or acquire a lot of gold.
I think it makes a lot of sense to reward Support players by cutting their LP losses by maybe 1/3rd in ranked. If you lose as Support and normally you'd have lost 21 LP, make it 14 instead. This takes away some of the risk involved for people who might suck at Support (like those who got auto filled) and also will make more players want to Support at the same time.
Obviously, there would need to be a serious consequence for players who do not play their role after queuing up as the Support.. But anyone who does this is really just harming themselves as they are more likely to lose anyways.