Supports: cut them loose from bot lane.
The way roles work makes it that we usually know what to expect when we jump into a match. In a lot of ways, that's a good thing. On the other hand it can be considered abusable and can make you feel stuck if you main a role and deal with lane bullies, hyper mobile playmakers, free ranged harass and so on. Once things start to go wrong, you're usually doomed to sit things out on your own during the laning phase.
This is where the support role comes in. A support should have the freedom to go where he's needed. For that he needs the flexibility to change lanes (and even to the jungle) at will. Start mid or top, help the jungle in the beginning, change lanes inbetween to for example help your bruiser catch up to a pesky ranged harasser or help your mid survive against an assassin.
The support role has the potential to be far more fluent in its position than being stuck with an adc bot. I'm not talking about all supports, just a niche of supports that can fulfill that role. Currently, the closest we come to that is Bard. He doesn't quite do the job though.
What is needed to make that work would be adc's who can hold their own 2vs1, more tower safety so people can respond to the changing numbers when a 1vs1 suddenly becomes 2vs 1 or vice versa, supports with either enough mobility to quickly change lanes or some mechanics to gain exp and gold while travelling.
No more cheese picks having free reign over their lane until laning phase is over. No more teammates feeling abandoned by their team because they go counterpicked and have a terrible time in lane. No more 2vs2 as the absolute standard in bot lane.
The support role already has some macro aspects in its core gameplay. Why not go multiple steps further with that and make some supports truly team oriented as top/mid/jgl deserve them to be?
PS: this is just a thought and not remotely fleshed out or thought through. So please let me know what you think and if you like the basic idea, what you would do to make it possible.