Since most other things can be placed in Zeus (such as clothes, hats, helmets, etc), why can't backpacks - unless you place them in an ammo box?
It seems odds that I can give players sunglasses, but not UAVs.
Since backpacks include things like dismantled UAVs and HMG, it would be useful to be able to place them lying about.
They should be added under the Units>Empty>Other category.
Play as Zeus, browse to Units>Empty>Other...
No backpacks!
If your unit is not using a logistics script, backpacks are the only way to get bulk quantities of certain supplies into a helicopter or MRAP. As Zeus, I can create a crate full of sandbags, but without a logistics script or addon, my light infantry unit won't be able to load it into a vehicle. If I could create a backpack full of sandbags as Zeus, they would have the option to either load them manually into the cargo of the vehicle or carry them on their back.