Some questions.
1. How will prisoners be kept with this change? The brig is currently centralized along with everything else an officer needs, it's a single location they'll need to return back to. Will they drop off prisoners and then run back to their assigned posting half way across the station? What if there's no warden or head of security? Are there expected to be holding cells in every department or will they be kept away for the duration of each sentence while they watch the brig?
2. Most of what makes a security team effective is their coordination. If security are expected to single-handedly hold each department, their effectiveness will drop significantly. After a few novelty rounds, I highly doubt that the majority of security players are going to be hiding out in their respective departments when it puts them at a massive disadvantage against any opponent who has the intention to use mobility as a strategy. If security are still teaming up to go and play aggressively, as they often have to against mobile opponents, won't this defeat the point of the suggestion?
3. Crew antagonists get a lot of leeway by not having security constantly breathing down their necks in their own departments. This really seems like it would change that and put a near constant sec presence in every department so long as the slots are filled. What are your intentions for the access given to the officers assigned to each department? Will they have full access to the department? Limited? None more than now?