While think level scaling could be done correctly in a game like D:OS with a few extra rules put in. I agree that putting it as the default runs the elder scrolls risk of lack of progression (hence the suggestion to put it as an option or difficulty if it were to be implemented).
At least in D:OS you are getting access to more skills, spells and talents, as you level so killing a scaled enemy would not be without benefit on your side.
If scaled enemies were put in I'd like for enemies to have a modifier, so that if you were supposed to be above each individual enemy by 2 levels they would always have a your level - 2 at max.
All that being said I'm not terribly attached to the idea, just one I'd like to see to resolve the issue the tactician mode had in EE. (Where you would actually be stronger late game than in easy due to the extra enemies to give you XP) making fights too easy in a harder difficulty.
None of this really addresses the issue of non-combat XP in a direct manor.