A suggestion for new RGM
I don't know if this would be feasible from a time or technical standpoint, but I think that it would be a lot fun to have a League throwback random game mode. This mode would allow to play versions of League from previous seasons for a weekend.
If it is possible to do something like this I believe that it would be an opportunity for newer players to experience some of the past and for long time players to reminisce for a weekend.
Now that League has a decent amount of champions that have been reworked an alternate suggestion would be to enable previous versions of champions for a weekend. Maybe even just a random game mode where items that have been removed or reworked are enabled would be fun.