They will tend to like neutrals and Cosmo-light more than strongly Cosmo MCs. Strong cosmopolitans will be more appealing to the priesthood and some of the other provincial factions.
Accepting a truce would be no problem. If the true heir actually embraced the Leaguer agenda and stopped promoting the superiority of traditional Shayardene culture and the Old Shayarin tongue, the Laconniers might reconsider the quality of the “proof” that had been offered for the bloodline.
If they get enough power, yes, it’s a big part of their agenda.
Yes – the canal, unlike the Ward, could be maintained by a cadre of dedicated self-fuelled wisards.
That’s basically how the Abhuman Guardian yega’a do it on the river that separates the Xaos-lands from their domain. As M’kyar will explain in G2 Ch1, Storms rarely ricochet down that far, and when they do they almost never drop an obstruction into the river before dissipating – but the Guardians are always ready in case they do.
It’s worth noting that the exposed area for the Abhumans is a tiny fraction of the Shayard-Braurach border, so the scale of the mobilization needed in Shayard would be very different. But it would be possible.