[legine]

Well it comes basicly down to the morale standad. If players apply todays standards it will be dissapointing if you apply an other standard. So I would not to much worry about.

If you check the romean army or the old chinese, they applied high disciplin. There is even one ancient book which is still valid in todays military teachings.

So i think you have to decide what kind of army they lead.
I'd orient myself on the disciplin value you base it.
Something like rome Legion or Sparta I'd give a 16.
a romean standard stroops 14 or 15, auxileries maybe 12, pressed troops 10 and less.
I would assume this values for fresh people. If there are arguments to reduce I would reduce by 1-4 points. depending on severity.

For each failed point I would assume 1% or if thats not working failed point sqared. that would mean miss by 10 and you loose the commnd of that particular unit.
With that there is some chance something happens, and the severity is of course higher if you have less trained troops.

I would also concider my next steps in the campagne. I think it is important not only to simulate but to tell a story. And the story tells you what limits you put in. Maybe more then 10% does not suite in the story, but causes enough trouble to be interesting.

For me it is really the question what do you want next. And that massivly influences the severity of the role.