As best as I can tell, the thrust of your post seems to be that they should introduce upscaled content, to supplement the usual options without needing to design entirely new fights. i.e. a level 70 version of Titan EX or Coil or etc.

Sure. I think, presuming that the numbers aren't too terribly hard to figure out, they could do that if they wanted to with relatively little effort. I'd personally love to see it. Realistically however, few players would actually tackle the upscaled content, judging by the fact that there's been zero outrage over min IL sync being non-functional right now.

Incentives would need to be added to push players to do them, but now you're "forcing" people to do "old content" and they would complain. You could also be looking at dev resources for armor models and such, though there are other incentive methods.