I could see the Mets being stupid enough to sign him fully knowingly that he might not be able to field within a few years - they do seem to have a fetish for old washed up Dominican players, you'd think they learn their lessons, but Omar simply doesn't.
I do think unfortunately, the best fit for Manny would be right in New York on the Yankees. They will need a DH, lots of money coming off the books this year, and with their offense way down this year... they will be looking to add a power bat - especially once they get outted in the first round of the playoffs again.
Manny has said a bunch of times he'd love to play for the Yankees, he may just get that chance shortly. It will be a real bummer to see a guy like that switch to the dark side, but obviously the forty million the Sox were going to give him for the next two years just isn't enough... so he'll have to seek higher pay else where.