I personally like the Belfast bridge for the size, its easy to get to the DOFF stations, etc. I guess this is a more "meta" answer, because the fleet escort's bridge doesn't look like the Defiants at all.
I agree that the belfast bridge somewhat fits, as it relays the sense that you're in a military-style ship and not an exploration or science ship. Honestly I wish they'd add new interiors like the belfast's that arent connected directly to a specific bridge (so you could have a simliar interior with a different bridge).
Other than that, I'd have to say the prometheus bridges fit the fleet escort very well.