I'm not really sure that using alien corpses to manufacture armor is a good idea, given that the only alien tougher than a power suit is the Sectopod. In fact all aliens except Sectopods and Ethereal Commanders are less armored than personal armor.
Using the corpses for other purposes, like the toxic ammo, is a better idea. However, I'm afraid that in near-vanilla mods this will be limited mostly to toys or specialty equipment, given how good the powersuit/heavy plasma combo is and how weak the aliens are as individuals. Sure, one could create items that are even better than vanilla items, e.g. a powersuit upgrade that uses muton cyberimplants to grant +5 to Firing or one that uses a sectopod wreck to build powerarmor with 0.9 plasma resistance. But every such toy one gives to the player makes the game easier, so a modder has to think about game balance too.
Mmmmm... Come to think of it... I guess it is time to create a mod that would rip the lascannon out of the Sectopod wreck and rebuild it into a man-portable superheavy laser. Say Power 100 and weight 20, so it is both weaker and heavier than a heavy plasma plus all the ammo you can shoot during a sensible mission. But it would still make a good endgame laser weapon....