This would help the USF captain and lieutenant model as well. In the weapon file under behavior, there is a option for "can be substituted." Not sure if this is the answer, but it could be a start.
I changed the value, but it seems that the value of "can be substituted" has no effect.
Aye, you would have to give the unit you dont want to use other weapons a dummy slot weapon.
This works when the squad spawn for the first time, but after I reinforce the model with the pistol, He adds the slot item to a random squad member. I did place the add_slotitem action in ebps of this specific model, but still adds it to the squad.