Since the RivTech guns were made in a special (probably underground) facility, I think it would be neat if a player could take over the facility. It would be patrolled by heavy SecuBots, turrets, maybe a chicken walker or autotank, and the player would need to download schematics from a very high level computer. If you fail to unlock the computer, there could be a chance of triggering a self destruct sequence. The player could either GTFO, or try to disarm it. If the player managed to get the schematics, they would need to have a high enough machinery/electronics skill to use the equipment. Maybe there could be a convenient training/operation manual somewhere. Since the player would have to be ridiculously kitted out to take over the facility, I think it would not cause unbalance.
Also, for lower level machinery, Iām sure at least SOME firearm manufacturing equipment survived. Like in the fancy gun shops for instance.
On a side note, why were ammunition vending machines removed? You needed a hacksaw/acetylene torch to open it, and cop bots would show up. I think they should be a thing again.