I'm in the process of designing a skirmish level game and differentiating factions by city is the mechanic I'm using so I'm partial to these developments but I can see how people see them as an unnecessary layer. I think it would have made a lot of sense to not have the faction allegiance abilities be as prevalent and instead stick to GA's and the thematic allegiance abilities based on city or realm of origin. It's more balanced, encourages mixed faction armies, and still wouldn't punish single faction armies if the ability sets were built correctly, in my view. That said, it is WAY too late for that in AoS given all the battletomes they've already produced.