I think the Molly-Outcast alliance is wobbly at best, as pointed out, Outcasts are neutral to Bretonia, which isn't gonna do their image any favours in Dublin.
Hessians and Mollys share a common background and a common enemy, and a friendship, at least, would be profitable for both sides in reducing Corsair expansion.
Rogues share technology with Mollys, and also deal with their smuggling (as they actually deal with pretty much everyone's smuggling, I could see Rogues with a much more neutral repsheet with respect to pirate groups..."Corsairs? Well, you don't like Liberty, so, meh...")
At a stretch, one could argue that Mollys, being originally a part of BMM, offer as much a threat to Gaia's ecosystem as the Bretonian mining corporation...
As for the Kusari/Bretonia war, Mollys are nationalists at heart, similar to the vanilla Rheinland/Bundschuh/GMG relations, ie: "kill off the bigger threat before returning to our internal squabbles", a stance I could see the Gaians taking up much more easily than "let's join with the outside aggressors, whose true agenda is unknown."
At least when dealing with the Bretonian government, they have a history and something to build on (Gaians even have a legitimate political presence: the Green Party, while the Mollys, admittedly, are not quite so well recieved...), whereas with Kusari, they would have to work up from scratch.