I'd ask WifS if they would do it first. I can just about guarantee it will fill quickly. As long as you enforce the rule. FWIW, I wouldn't even worry about MWR or tanking. Tanking is done to build a super team. If that super team wins the WS, owner is gone. As far as the MWR, you'd actually be better off with the guy who wins 50-60 every year but never contends. He fills a spot for eternity.
The only rule you'd need is "Win the WS, give up the team." And, as previously mentioned, I'd require some sort of experience to prevent, or suppress, the alias issue. If someone wants to run their regular name and fill a spot in another world with their alias so they can take the WS winner, that's good for WifS. Plus, as commish, you could give the WS winner to the applicant with the most seasons played without a WS and squash that plan.