The gun up thing makes sense. At The Mall I have lost count of the amount of times someone has come into a room with me in it maybe shot a mate and I had no chance so called myself hit before I got shot.
likewise I managed to clear a small room or two without having to take an actual shot.
But then that was all down to player choice, we agreed to surrender/call hit before getting a stinger in the knackers.
It wasn’t an actual site rule but made sense for all involved and caused no issues for the players involved or the game as a whole.
And regarding my dummy grenade mention, I have seen vids where an unprimed BFG gets posted through a door with a shout of “GRENADE” so all in the room are aware and stops people getting confused with old mk5s lying around.
I still think it’s easier for people’s ears, cheaper and easier than priming hard nades after each throw and stops the costs of second hand TRMRs going through the roof