Last resort? You make it sound like it's Bretonia's duty to clean Dublin out...
Be that as it may or may not be, if there's one thing Mollies don't like in Dublin, it's Kusarians. If there's two things, it's Kusarians and Bretonian Battleships - an assault vessel with a purely offensive purpose.
This is MR policy, basically: You come into Dublin with that, we'll make sure you don't come back.
We enjoy an unfriendly cooperation against Kusari, but bringing an assault vessel like a capital armour eight Dunkirk into Dublin is something we simply won't stand for. It's going over the tenuous line we keep, because there's no realy reason you'd be in there except to attack us with it. (Speaking through an in-RP Molly perspective here.)
Sorry if I seem intolerant, but a battleship is way over the line, and Mollies won't tolerate that.
It's the ultimate symbol of Bretonian oppression and power. We're not going to let one survive entering Dublin.