I like the idea
behind the reposes, but the modeling work itself seriously detracts from any visual interest gained.
With the exception of the backpack on the 2x H.Bolter marine and the left bicep of the biker, every single sculpted section has far too much bulk. The key with resculpting bits is to start thin, so that detail can be added in successive layers. If you start with a core the same size or larger than the original bit's thickness, you'll never be able to keep things in scale.
Looking at the arm of the assault marine and all of the resculpted limbs of the reloading
ML marine, you should also be wary of the dreaded "noodle limb" (also called "spaghetti arms," but we've got a leg to contend with, here, as well

). Humans and power armor alike are constructed of rigid sections of a determinate length connected by flexible joints - giving too much general curve or ignoring normal proportions gives limbs an incredibly unnatural and awkward appearance.
Personally, I'd chalk these up to experience, cut away what I'd done, and try again, this time focusing on maintaining proportions (both by starting thin and working up to the proper thickness and by paying special attention to the length of limb segments and the position of joints). Mold lines and sprue attachment nub removal would also do these a world of good. At the very least, they've served as a learning exercise. Sculpting is tricky and the only way we get better is practice.