I have some similar ideas. A ammo trunk is one, some times you give your troops weapons
only to get there and find you need a rocket launcher and don't have one. So the ammo trunk
would work like something like this it is a small robot that can carry up to four weapons
depending on the size. Or you can have it carry extra ammo for your troops.
I think it would work best if you are facing lots of robots or heavily armored troops
that need different weapons to take down.
Or a weapons platform that you can swap out the weapon that it has (only at the base).