This could easily be dealt with by intelligent dungeon placement. Dungeons closer to towns/roads would generally be less challenging. This reflect the idea that most settlements are equipped to deal with larger threats in their domains. The further you travel into the wilderness, the more likely it is you encounter higher level creatures and more challenging dungeons. There might still be some regions that are more challenging, but town areas within those regions would still be relatively safe. Further distinctions between different dungeon types (bandit dens are more manageable, daedric ruins more challenging) and it'd be clear to the player where they can risk going and where will require greater preparation.
This greatly expands the number of "beginner dungeons" by spreading them out across the entirety of the game world instead of cramming them all in the first region the player happens to find themselves in.
Exactly, people forget that Set Level, smart dungeon placement has always been a traditional, tested, and proven model for making challenging and fun RPGs with rewarding exploration.
The Rat Cave right near the starting town is low level, and the Mother Rat at the bottom has a nice level 5 weapon. The Ice Giant Cave at the top of a mountain 20 minute hike away from a small outpost, is level 35 and has an Ice Giant Matriarch at the very bottom which takes another 1hour of combat to reach etc... The first level of the Ice Cave is 20, the 2nd level down is lvl 25 and so forth.
The whole "What about when I make a new character". I mean, does that matter? The content is the same in SKyrim, There isn't going to be ONLY ONE dungeon for level 5s.
Scaled, or leveled, the number of areas is fixed.
I agree that a MIX of scaling and set levels would be nice *if* it worked the way they promised