IIRC, Dunnu being a fortified settlement and as well a regional administrative center in rural estate, I suggested the idea of the Dunnu being directly an Administrative Center replacement. With its own fortifications, and eventually a bonus.
Currently Adminitrative Centers are not fortified, don't have any specific adjacency bonus, there is no AC replacement as EQ, and it had the aesthetic of a rural estate.
So it's maybe a crazy idea, but it would be really unique, as expansionist, to attach your outposts, which will become a Dunnu (basically a better Administrative Center), to consolidate your territorial possessions in the ancient era.
The influence around Administrative Center could be the Legacy Trait. I mean, additional movement point is a good bonus, but a bit blank, and unnecessary for the cool Assyrian Raider imo.
And from my point of view : building a fort near an outpost don't look that useful, when there is no saboteurs in this era + it interfer with the uniqueness of Hittites which can spawn units on their unique outposts.
Well, just my thoughts, I am not game designer. But I feel than most of the other Ancient cultures feel a bit more well-handled and coherent than my dear Assyrians in term of kit and flavor ^^