Here's another argument for just duplicating and deletion of weaker units (read: archers and axemen). Essentially, land = power = gold = science. The quicker you can control more cities, the better your outcome. Think of my Sha Mo Ke game which I was going to win until the bugs. I expanded to the required number of cities to get science and culture going, and that's just with 1 strong unit (the 12 strength swordsman). What would make it much harder would be if there were more defenders. But if you deleted the swordsman (which is the case in the 200 AD start), it will be impossible to win at all.
Same thing goes for Sun Ce and Liu Yao--if the latter had more defenders, Sun Ce would have a much harder time conquering his traditional territory. If Sun Ce has more defenders but the SAME number of attackers, the difficulty would still be there for Liu Yao, but at least it'll be possible to defend (as opposed to right now when Sun Ce has virtually an army that can crush anything until Yizhou).
Right now, if I rolled a start without ANY horsemen or unique units (Danyang or Jizhou), I would just reroll, which kinda defeats what you are trying to achieve.
So how about adjusting the code to allow only for deletion or duplication of the weakest 3 types of units (archers, crossbows, axemen) for everybody, not just the traditional strong powers?