You could try calling up SPG to see if they'll do miles and points for the Osaka Sheraton Miyako.

We got a few nights at the Tokyo one (cat 3) for 2,800miles a night plus $45 - the Osaka Miyako is just category 2 (1,600miles + $30)

There's a glitch on the new *wood website which means you might not see the cash & points availablility online. Youll have to call.