[Pocus]

Harass or skirmish would be a better order which define well what they should do. Basically, a fire and flee, where units stay with your army win the province, would solve elegantly (understand not to bothersome to code I suppose) the problem.

I'm waiting for the response of Psitticine in fact, perhaps it works like that in doms II.

Velites cant be used as hypaspysts, because :

hypaspysts have a very high morale, meaning that they are used throughtout the game to bolster troops with weak morale, whereas velites are average on that.
But mostly because hypaspysts are worth their cost, as they have a high defence. They are produced 2.5 faster compared to hoplites. On the other hand, for nearly the same cost (9 gp versus 10 for a legionary), you will get velites which have an average morale, and are produced only **slightly faster**(+30% faster compared to the ( lowest cost in resource )legionary, which is anyway far better than a velite).
So in essence there is no real justification to choose building a velite compared to the lowest (cost in resource) legionary.