I personally still believe that in a realistic manor any group should be allowed to call in for reinforcements in a crisis event. This is inclusive of ALL groups, i.e if group A attacks the UNMC who only have a few on at the time, they should be allowed to call in for those soldiers asleep at the barracks or on leave in Sofia to be called in. The same goes for any gang who owns a gang base, if you are big and wealthy enough to own these militarised facilities then I have no problem with you calling in back up from your men who would realistically be manning your rebel camp/outpost/base . Same goes for the police, if the federal reserve is being broken into, special constables, reservists, off duty officers would be called in. I believe any group attacking the building of another group should expect it to be a tough cookie to bite. Personally, when I was in the UNMC, we didn't care if the full 40 cops were at the HM, we'd take the challenge, sometimes win, occasionally loose, and move on. In the same light, as a cop, I've never expected to go up against anything less than the full 87th Division on the UNMC when launching an assault on their military base, and have no issue come win or loss about the numbers they could throw at me, as I expect nothing less.
I also see issues regarding the HM Zone. If I am an officer who is set up outside the zone (As I wasn't on before the blasting charge went down), I could watch a cop on the border inside the zone be gunned down but 5m in front of me and be able to do nothing about it. At the same time, the rebel who shot him would then have to very awkwardly stand there and not shoot me (he should definitely be able to shoot me!) until he crosses an arbitrary line. The same goes for any rebel reinforcements, they too would have a very awkward time also. Another point is that say I am a sniper (police,rebel) and I am on the edge of the zone. I am 100% protected from any attacks from behind, as the attacker by definition would be outside the zone shooting in, and breaking rules. If you are skilled enough to be able to shoot from a long distance, good on you I say, more power to you for being skilled enough to do it, but at the same time, If I'm sneaky enough, I should be able to creep up behind you and shoot you, or, conversely, shoot back at you from a long range also If I can pull off the shot. The best way to describe this would be like taking a sandbox to the beach and telling your kid "hey son, you are only allowed to play with the sand inside the sandbox".