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 Urban 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.