There'd have to be some kind of 'tier' system or something. I don't know how it'd work other than eyeballing it, but like...
You can't let somebody take a 'highly sought after' character as an alt, IMO.
Like if you play Emma, your alt needs to be like...Mercury or Magma or something. ETA : I also think there'd need to be proven activity before giving an alt. Like goddamn, if you want an alt you can fucking prove you're going to play the character you already have.
Anyways. I'm totally okay with Marvel heroic as a 'reference' thing. IE you can do +sheet so and so and see their numbers and stuff for comparison. Not a fan of actually rolling stuff.