Currently, the defensive garrisons for many races in IE look to be placeholder for the early Beta. We're already expecting this to be fixed, but my suggestion is for some (though not all) subfactions to have more specialized garrisons related to their lore and gameplay specialty. In WH1&2, Wurrzag and Skarsnik were given unique garrisons much like this, tailored to their subfactions, with Wurrzag replacing all of the orc and goblin infantry with savage orcs, and Skarsnik replacing some of the orc units with more goblins. I want to see this come back, but for more races and incorporating DLC units for the relevant factions. Holdings of the Huntsmarshal's Expedition should be protected by huntsmen and archers, the Cult of Sotek should field more red crested skinks, Grimgor hates goblins! Kick 'em out! And then there are the Skaven.
I actually want to take a moment to make a special appeal for the Skaven. More than any other race (second only to Chaos, with Greenskins maybe being a not too distant third) the Skaven have been known for factional division and its implementation through its roster (still waiting on a generic lord option for Clans Pestilens and Moulder btw) The way they defend their territory should also represent this. Mors and Rictus, being Warlord clans, ought to be the baseline for the Skaven, relying on sheer numbers to overwhelm any interlopers. The four Great Clans however, should see more of their specialty units defending their territory. You just know clan Skryre would set up a few ratling guns and doom flayers in their nests.