Well, I said this in some of the previous topics on the same subject, but what we could have, as one topic, is differing levels of metallurgy.
That is, dwarves right now seem to have more modern blast furnace methods of steelmaking, and produce "pure" steel of modern quality.
Instead, we might have a "base-level" wrought iron, crude steel,
wootz steel, damascus steel, and dwarven steel. (The last of which having the properties that are associated with current steel.)
Once we get the capacity to properly make items out of more than one material, armors could similarly evolve, starting with the likes of scale or lamellar armor and four-in-one mail, up through six-in-one mail and splint mail, to eight-in-one mail and field plate. Even leather and cloth armors were improved through different hardening techniques.
We could have crossbows that diverge in their composition for providing either faster reload rates or heavier impact, with pull-lever-crossbows and repeater crossbows being faster, and windlass or cranequin crossbows or arbalests providing heavier firepower at the cost of speed. Recurve crossbows can add velocity regardless of loading method. Compound crossbows could be constructed to allow for greater total power, at the cost of requiring stronger dwarves to operate, or requiring a slower winding method.
All of these could largely just be evolutions. (Nobody wore scale once they knew how to make field plate.)
These don't have to be all military, of course, music and poetry and such are fully capable of "evolving", although there aren't as practical a set of results to show for such things.
Ceramics, as well, is the source of technological progress, with porcelain being far more difficult to produce than this game gives it credit for. (I made a longish suggestion on the topic before it was actually put in the game. Porcelain actually needs temperatures hotter than magma to be properly produced, and was responsible for Europe largely sending nearly all its precious metals along the silk road to obtain all the porcelain they could possibly get. Porcelain probably should require special forges which are powered to spin fans that provide the proper high airflow to burn enough charcoal to properly make porcelain.)
The main problem with these is that there is no particularly good reason to bother with such things, especially as there is no reason to bother with high-value luxury goods when simple food roasts or bins of cloth are generally worth more money than you can ever spend. (Hence the whole "Class Warfare" thread built to solve that very problem...)