Please don't harass people for ignoring/disliking the story

[Absimiliard]

The reason the Weapons exist in the first place is because they're based on already existing monsters - the Ultima Weapon, which is a basis for the others, is literally just a giant lizard with armor grafted onto it.

Ultima Weapon is a biotechnological weapon, but its internals do consist primarily of machinery. It was not, based on the information we currently have available, a lizard with armor grafted onto it. Were I to hazard a guess as to the reason for its shape, I'd tend to think the Allagans based it on the dragon-centaur things responsible for summoning Zurvan.