Thanks for bringing up the romans, theyīre somewhat of a specialty of mine.
The legions were supplied by state owned factories after Augustus had reformed the military.
These of course made equipment according to the nature of their legionīs frontier and had their own styles.
To keep logistics as simple and therefore as cheap as possible, supplies and amours were acquired locally.
The variety in equipment IMO was a result of the constant redeployment of the legions and the simple need to reuse any viable equipment.
Thereīs this one new recruit whoīs bigger than all his peers? Equip him with long chainmail from storage.
This helmet doesn'tīt really fit? Try out the older model we have in storage.
If we go by history, the wealthier the state is, the easier it can provide arms and armour to its citizen soldiers.
F.e. Antigonid Macedon supplied its Phalangitai certainly with Sarissai and possibly Aspides,
if we assume that any new king issued shields with his name on them as Sekunda suggests.
Most of the time, states simply weren't wealthy enough to pay for their soldierīs equipment,
heck even feeding them was often troublesome.
The Dalian Spear-/Swordsmen are representative of Daleīs soldiers when itīs at its peak.
Vastly rich through trade, and some of the best smiths of ME right at their doorstep.
The Dwarves of Erebor surely were able to mass produce armour,
which makes it way more economical if the state provides equipment through bulk purchases.
Iīm applying the same principles to them as to the Romans,
but with simply one supplier and no vastly different frontiers.