Frankly, I don't want to be penalizing distant wars as much. We used to penalize them much more—and I'm pretty sure you were around for that.
The problem with large alliances has very little to do with fighting enemies very far away.
More importantly, I'm happy to have 2 allies fight a realm that's only close to one of them. I'm not happy to have the entire continent gang up on one realm, even if that realm is centrally located so they all have short marches to it.
In any case, what you suggest, as I said, not a new restriction, but a return to an old one—and people have both complained bitterly about it, and done their level best to find ways around it, for many years now.
I don't yet have a better answer as to how to prevent entire continents from locking themselves up in alliances, polarizing to two warring factions, and/or ganging up on one or a small number of realms.
