I understand where you're coming from here, as it's not ideal for the service crew to be totally sectioned off from the antags, but I think there may be some potential here for the opposite to occur. Like Lilah mentioned above, most of the time when things are going to hell around the outer edges of the ship, people end up congregating in the central ring. Admittedly, I'm far from a seasoned antag player (and if anyone that is wants to weigh in and correct me on this, please do), but it feels to me like the design of the ship strongly discourages you from trying to push through the central ring or try to take hostages there. It's wide open, and there are entrances to it from various departments all around you, as well as both above and below. If an engagement does break out there, there's a high potential for things to get extremely chaotic. If, on the other hand, you manage to find your way into a space full of unarmed potential hostages that also offers you a tactical advantage, you're much more likely to choose that option. This could also make things more interesting from Security's standpoint; if things go down in the central ring, you have a million and one ways of getting in there to try to resolve the situation. But if the place the crew gathers is slightly out of the way and has fewer entrances and exits, then you have a trade-off to consider: do you leave some of your forces near the bunker to make sure the crew is well-protected, and risk being taken down in engagements elsewhere in the ship? Or do you go all-out on the offensive in the hopes of getting rid of the threat as soon as possible?
I'm sure there are ways to address this issue that don't require the ship to be changed in some way, but I don't think it should be totally ruled out as a viable option.
I'm also thinking about quantity vs. quality here when it comes to antag encounters during high-stakes events. Catching a glimpse of big scary person with gun and immediately running in the opposite direction is exciting, but it's not often engaging. If the crew is stuck in a room with the bad guy, it opens up more potential for the kind of depth that is often lacking in the current model of 'spend an hour hunkered down in the central ring, and then when you finally get more than a brief glimpse of the enemy, it's because they're a corpse'.