The only problem with the Marmit Stormtroopers that bothered me was the fixed ankles and lack of posability. It finally overcame my better judgement, so I took off the lower leg armor, and cut the feet off with an exacto-knife along the moulded seam. Then I cut about an inch or so off both legs, and attatched severed legs from spare figures, of exactly the same length, except with articulated feet. Then I glued the body-stocking thing back into place, painted it white, and put the shoes back on the feet. Took about 20 minutes, and done right, the joint looks perfectly natural!
So, voila, moveable feet, and you wouldn't believe how much cooler they are to pose now! Running, crouching, etc.... The only other beef I would have with the Marmit body would be that the elbows don't bend far enough, but the way the armor is, I don't think you'd be able to improve the range of motion much anyway.