I have an idea.
What about separate character slots you could choose to use where theres absolutely zero limits on costumes, powersets , or power pools everything can be used without being earned, and you don't even need to have a target to use attacks, but those characters have no combat level and can't attack, or be attacked by anything.
This way, those that want to costume and all that can as much as they want without worrying about trying to grind something out on that character.
And those that want to play the game to earn things and enjoy a sense of acomplishment can do that on the regular slots.