In case this has gotten lost or forgotten over the years, some time ago we linked distance from capital penalty to apply equally to allies' capitals, so if you're conducting a war in support of a friend, you shouldn't have any problems with that particular nuisance.
(I recognize that there are other impediments to long-distance campaigns, and have Thoughts about how to address them, but as yet no solid Plans.)
I am not a fan of promoting making too many allies to be able to maneuver through Dwilight.
Also, to even travel through the inner seas, you need to ally with either Astrum or D'Hara due to their locations.
