Ability To Change Existing Save Into Custom Mode

[Literally Who]

I am pushing this cart way ahead of its horse, again, but just to be safe - I wanted to ask in advance to make us able to convert an existing save into a custom mode save, if possible. Primarily because I wanna hold onto that sweet McMansion I poured so very many hours into without committing to a total reset in the form of NG+. Ironically enough and despite the intended theme of the game, I'm actually quite content with my 100% save, I'd just like to pretty it up with a level cap and an XP adjustment to make it possible to reach said level.