The problem with that, imo, is the extent to which the judges take themselves out of the equation by handing out scores within a very narrow range each week. Given how much hinges on the audience vote, I think you could hand him the trophy at the start of the season regardless of how well he dances. Particularly since I don't see any reason he couldn't dance very respectably if he put forth the effort.
How about some of the women from the Prince days...like Sheila E, Vanity or Appollonia. That would be fun... and they are in that category of "no longer famous, but we still know them". Some of the 80's era supermodels like Christie Brinkley or Beverly Johnson. Jennifer Beals from Flashdance... she really wasn't the one dancing in the movie. Kim Cattrall from Sex in the City. Ok... I think I have just declared my age by my choices... but point being, stars that are interesting, and may be looking for work/publicity.
Adam West would I'm sure be at LEAST good for a laugh. He has a sense of humor about himself, he'd probably have the right attitude you need for DWTS....it's always better when they're willing to poke fun at themselves.
I realize this'll get a "who?" from many of you, but I think Gerald McCoy would be a really good fit for the show. There would probably be an awful lot of, "oh, great, a Warren Sapp redux" if they cast him, even though their personalities are actually quite different.