...However, since this character was never actually stated to be the commanding officer of the Prometheus, and indeed Seyetlik himself appeared to fill that role, we are not forced to believe in any particular backstage explanation or real-world backstory.
Lt (jg) Piersall could simply have been the hapless underling who had to cope with Sisko in a situation where the top brass of the ship was embroidered in Seyetlik's mad activities.
I have no real objection to the Prometheus having a small bridge, though. We have already seen that very small ships may have very large bridges - the Grissom, the Tsiolkovski and the Equinox are examples of the "guest bridge of the week" being if not larger, then at least more spacious-looking than the bridge of the much larger hero vessel. And yes, the standard TNG/DS9 guest bridge set in all its variations seemed to feature corridors reaching to other rooms on the same deck, suggesting a large if partitioned command center, and actually making the nerve centers of Kirk's various ships look smaller than any of the guest ones.
Timo Saloniemi