Talk to your lawyer. Seriously.
You want a custom license that fits your situation, and the quickest way to get one like that is to pay a lawyer to write one for you. Also, it's probably the best way. Don't try writing it yourself unless you are a lawyer, which I guess you aren't.
What it sounds like what you want to do is to offer an explicit "character/universe license". Which allows people to use your characters/universe as they see fit. That's an interesting idea. But yeah, there isn't anything like that that I know of. Probably because most free culture licenses are written for software generally. Other types of work haven't really gained a large following for licensing stuff under a free license.