as to the chaledonians being a long lost region of a larger nation of wich the fjordlandrs were part, from what we know of the chaledonian history, we know tat they have been isolated since before the great environmental disasters that brought low the rest of the world, but because of their resources, they didnt suffer with the ecological destruction of the rest of the world, in fact as i recall, they didnt even notice. when a fjordlander showed up there in an airship built on the gabrielan archetype, they realized they could cross the obscenely treacherous pass between the island of chaledon and the mainland by air, and when they did were appalled by the ecological destruction they found in the rest of the world.
what interests me with all this is how the merchantile guild would use the relative defecits and strenghts of the various nations to make a tidy profit, and with this profit, i imagine fund and create a powerful fleet of airships both of their own design, and also likely a smattering of foreign ships as well, both adapted and if need be, hired outright.
as for their involvement with the yesha, there's no reason to only suspect their involvement with one another, the yesha are the largest faction on the map both in terms of naval power, size and presumably raw industrial resources (and therefore presumably a large number of manufactured goods as well) OF COURSE they are trading with one another, the mercantile guild could not pass up such an opportunity!!
The MG is a group of traders so close to psychotically obsessed with gaining wealth through trade that i wouldnt doubt that the other factions couldn't help but look at them askance. they aren't EXACTLY warmongers, but they are prepared for EVERY contingency, and prepared to make a profit no matter what happens. the profit margins for proviting warships to warring states would undoubtedly be astronomical, and as such, we must assume that the MG would negotiate EITHER non agression treaties so they can sell war suplies to both sides for a HUGE margin, or cast their lot in with one side or the other either for a lot of cash (whatever cash is in this world) or for some kind of OVERBEARING advantage over a faction that harried them.