It's called Ruby Weapon because that is what the same mecha-like being is called in FFVII. The other main WEAPONS in FFVII are Sapphire weapon, Emerald weapon and Ultimate weapon...

We see the Rean woman and the Rean man talking to Giaus in some other screenshots. Given the normal Garlean attitude towards non-Garleans, I doubt those two are with Garlemald in particular. It would make more sense for them to be people Gaius knows of since he really does not care about what race or culture people are from so long as they can do their job right.

As it is, we don't even know if Ruby Weapon can be piloted like a mechanical can. The weird Ultima-like Weapon Estinean fought had someone grafted into it practically...