I HAVE AN AMAZING IDEA THERE BROS! I HAVE NO IDEA HOW I GOT IT, I WAS SIMPLY STARRING AT THE PC SCREEN AND SOMEONE SHOT IT TO MY HEAD!
"Cough"
Anyways, on the serious side...
How about Gang HQ's would have a limited stock size? Gang HQ's stock size would depend on how big the area of the HQ is, every HQ would have bigger/smaller stock size. For example
[LOL] gets a HQ at the biker shack
Biker shack is indeed a small place
/c hqstock
Weapons that can fit in HQ:
10 Shotguns with not more than 1000 ammo
5 Assault rifles with 500 ammo
15 Hand guns with w/e ammo
Basically it would make it a little bit more difficult to criminals, since now they have like 5000000000 stubbies in their HQ's and dont give a shit

And after all, it would increase roleplay
P.S
SOMEONE SHOT IT TO MY HEAD!
My head hurts