If you are running the league just use your brain and only let suitable people in. How hard is it to use your brain?
Are you trying to tell me I am an idiot? How should this help the suggestion?
A salary cap could also be programmed that way that lineups over/under a certain amount cannot be submitted - how about that? That way it would be irrelevant if someone bought a salary behemoth that would make a team go over the cap, as long as a lineup according to the league rules is possible.
Use your brain to add something to the discussion instead of dropping some useless crap please.