Ultima is made of technology, not energy - he absorbed the Primal's Aether and gained their powers. When fighting Ultima, each Primal slowly leaves Ultima and returns back to the Aether like killing any Primal did before him. So Ultima really couldn't do that kind of thing, especially since Ultima is a product of Allagan technology which has shown to be vastly superior to Garlean's.

Also, all the monsters in Coil (excluding Twintania) are machines themselves, so we'll likely see Ruby Weapon and the like in there.