I think I'll start referring to editions based on Batman actors...
"1e" = D&D West
"2e" = D&D Keaton
"3e" = D&D Kilmer
"3.5" = D&D Clooney
"4e" = D&D Bale
"5e" = D&D Affleck
... and this year's books are D&D Pattinson
There's a whole different feel when the Prime Material Plane is the hub of the Outer Planes. It makes the cosmic neutrality of old school Druids and major Greyhawk character more understandable.
I go by the idea that characters with class levels are extremely rare, and have some kind of destiny. They're certainly not common enough to constitute a societal profession. Adventurers have, or will have, a heroic or dark legend tied to them.
If I ran a FR game where the planes came into play, I'd probably use the World Tree. Also, for the record, I prefer the pre-Deities & Demigods version of of the Great Wheel for Greyhawk. :p
This is what I've been contemplating in my nascent heartbreaker. Roll the ability score math into proficiency bonus, and have skills be background based.