First thing, enforce the rule! You had mentioned that you'd put gravity feed hoppers on anyone shooting too fast...I never saw it happen, but you gotta have enough refs to enforce it. Second, you need a chrono ref that can confirm electros are capped AND locked...slow and cumbersome...and your still gonna have folks that cheat it.
I know a few players love the restricted paint ideas, and pump only games, but I think you'll find more players want to have the ability to shoot as much as they want...you gotta find your happy medium.
I think the most sure fire way to restrict would be to go mechanical only...you'll still have a lower turnout, but it's less restrictive on "trigger time". I personally would be frustrated playing a game that I had to wait for a respawn to reload!