Full Metal Alchemist fits in elemental sort of a lot better than mech warrior, since you could replace magic with alchemy and add new items/resources for doing alchemy. The military is just people. Homunculi can be special creatures like a sovereign/champion mix.
Mech Warrior would for the most part be entirely long range combat, you would need to mainly redo everything, new resources, new structures, new models, I suppose you could replace magic with special orders, like orbital bombardment, or special attacks or abilities that they would not be able to use often.
