I don't think they can be unified
Though I think 4E brought a lot of genuin improvements to the game that a lot of diehard haters of 4E tend to overlook.
Just "Resting" was something I considered to vastly improve the game. Spells that don't run out as a spell caster vastly improved the game. Having attacks you can do as a Fighting class vastly improved the game.
The fact that 4E done combinations of might AND magic within one class better then ALL DUNGEONS AND DRAGONS COMBINED is something to be said.
You cannot get magic items at a shop except if you're in some sort of exception area (mages college for example). Anything better than a +1 now requires a backstory per the rules. So while common magic items are certainly possible....they're going to be a crap ton of work if the GM does it right.
That sounds setting explicit... however knowing them they are going to enforce it across all settings somehow.
Even though... you know... any Hero worth its salt should have a lot of magic items seeing as even in "Low fantasy" worlds there are a big load of magical creatures and quite a few powerful mages.
I cannot think of many settings where magic would be so rare. Certainly not Ravenloft, Forgotten Realms, Darksun, Oriental Adventures, Ebberon or Planescape.
Is the main setting Greyhawk? Ok maybe Dragon Lance, I mean I know they have official magic schools but maybe you could justify next to no magic especially given that there is a hard enforced level limit.
Anyhow limiting magic items to me isn't because they want to make "magic more magical" but more likely to remove magic item gathering as a required part of the game. Besides I never found how common magic was to ever lessen its magicalness. Though that is because I find rarer magic to be less magical and for good reason.
Mind you magic in dungeons and dragons never made sense from a societal point of view, but I always figured it was because they were just focusing on the aspects of combat and left the spell that could rejuvinate fields alone.