Brainstorming a setting for a Tier 4 classes only game

[Nifft]

As a thought experiment, I've been looking at the revised tiers list and been thinking about what such a setting would look like using only one tier for all the available classes. Tier 4 (minus Dragon magazine and UA generic classes) inspired me the most, so I went with that.

Classes: Incarnate, Shadowcaster, Rogue, Barbarian, Scout, Spelltheif, Paladin, Ranger, Ninja, Adept, Fighter, Marshal

How about Dragon Shaman, Warlock, Psychic Rogue, and Hexblade?

What are your thoughts on how to incorporate the Paladin? Do you have any ideas which expand on those outlined above? Or when you look at this list of classes does a completely different setting come to mind?

Take a page from 5e and have Paladins derive all their power from their Oath.

(This also allows you to have variant Paladins with different Oaths.)