if you place an empty Praetorian with Zeus and put a unit in, it says the vehicle is full!
I do understand that those staticWeapons are typically unmanned vehicles, but for mission editing purposes one of the commands above should work to keep things streamlined. Every other staticWeapon, which is listed under "turrets" in 3DEN can be manned with something like the above, only AA are excluded, which makes things complicated.