Hi Mikael!
I suspect you may be looking for the functionality I was asking for in this topic: Specialising value set items?
That topic was about specialising DV_CODED_TEXT, but I’ve done some testing right now, and it looks like AD doesn’t allow changing any value set items from the specialised archetype in either DV_CODED_TEXT or DV_ORDINAL. It only allows adding new items, and not even constraining out value set items like you can in templates.
In my opinion, you should be allowed to change or constrain these out. Making sure you’re within a reasonable semantic refinement of the original item is your responsibility as a modeller.