I don't know that we've ever talked about it here, but it's certainly possible. Just get a few figures to practice on till you refine your technique. You'll no doubt totally ruin one or two as you figure out the best way to take in apart and get it back together again. I loved the old (vintage 1980's) 3 3/4" G.I.Joes because they were held to gether with a screw and a rubber band. I figured out as a kid how simple it was to unscrew it and mix-n-match the body parts. Somewhere I have a cheap knock-off guy that my cousin took apart and swapped the arms for the legs! It's a weird looking little guy but it's pretty cool. I had him standing on my desk for years before i got married.
Anyway, having not actually seen how these figures are assembled, I couldn't give you any specific advice. But if their like the older playmate Trek figures of yore then they are hard-ish plastic parts with the limb joints secured by virtue of the fact that the torso front and back halves are stuck together. I'm not sure if it's with superglue or some other adhesive or if it's by means of sonic welding (which I suspect but haven't really looked up, so I don't know). Either way, the torso is closed pretty tightly and you'll have to figure out the least destructive way of separating them. That's why I recommend getting extra toys to hack and slash and figure out what you're doing.
Good luck!
--Alex
