Thanks man, I love removable helmets, so I try to do them when I can.
You're right on the base figure, here are the parts:
BBi Elite Force Navy Seal Breacher - base figure
Vintage Biker Scout - boots
POTF2 Imperial Gunner - hollowed out helmet
That's a good idea about weathering him, but I kinda like him clean. I don't see these guys having too much trouble since the main Separatist forces have been destroyed and the rebels are not yet strong enough to put up much of a fight. I'd imagine it would be a pretty cushy job to be an Imperial Gunner ... at least until they die in the Death Star