Arma 3 does not have an option to select an unarmed unit for each faction in the editor.

This used to be in Arma 2 and was very helpful for mission making in selecting custom loadouts for units.

You could have a new header under the "class" menu for each faction in the editor. Like "Soldier (Unarmed)". Then in the "unit" header, it would have something like:

Soldier Unarmed
Soldier Urban Unarmed
Sniper Unarmed

The units would still have their Fatigues and Harness, but all other equipment removed (including hats).

It would be a relatively easy job in the configs to do this. Please consider it.