I'd actually swap out the Palisade (wood) instead of Market. The Castra offers a kind of defense against legions, and it made the cut for the expansion precisely because palisade was getting diluted. Of course, Castra has a different impact on the game than Palisade -- Castra does not reduce the benefit of playing a legion, it just softens the blow on the victim. So, expect a more militaristic game with Castras replacing palisades.
I agree that cutting Bar is probably right, as it probably is the least influential rubble building on overall game strategy.