@Skinner35I guess it depends on where or when this RP is set. I guess if someone is playing Eraserhead then this will be set in the same area as the main series, but does it take place before or after the events of the series?
It also depends on whether the villains are part of a larger organisation or were previously separate but form a group as part of the RP. If it is the latter then I like the idea of a villain, whoever ends up being the leader, seeing the success of the League of Villains and deciding to copy them, recruiting everyone else into their group.
This new group could then set their sights on the school (if people are going to be playing students) or on some hero group they have a grude against.
In terms of character creation, what sort of power level are you expecting? We'll be less powerful than All Might or All for One obviously, but any limits you want to set. Any power that you don't want to see? I have a few ideas for Quirks but some of them might be a bit overpowered.