Marriott do status match, here is a recent thread on it (there are others if you search);

http://www.flyertalk.com/forum/marri...challenge.html

Chances are they will match your status to plat in return for a number of nights. The best challenge is one where they 'promote' you to Platinum at the start of the challenge, and then you get to stay Plat if you stay for X nights in 3 months. With your travel patterns I would push them for that.

They will potentially want to see a screenshot of your account status at the other chains.