In Daggerfall's case, you won't need huge storage spaces because it is procedurally generated. Just like Just Cause 2 which is partially procedurally generated, partially handcrafted.

I personally want to go for 4x for creating some huge spaces while using the same amount of content because I find it a bit crammed, I like outdoors. This land data shouldn't make much difference in size. There will be technical problems but I would put these technical problems as top priority. When you can work on the same engine for ten years, you should be able to deliver. If necessary I would ask some help from Cevat Yerli.

I saw your post earlier. I agree. 4 times the size would do great things for a gameworld. 8 Would be good, but would require a most exelent fast travel system.
-Mountains are twice as high, Fields are twice as long. Makes vistas seem more amazing. Mountains Would look Like mountains, Farmland Might even begin to look big enough. Lakes could hold surprises and seas could hold monsters.
-Cities Would not Feel like glorified towns. Furthermore, Each city would be able to contain multiple guilds without feeling Like it's meerly a quest hub and contain more than one temple. Such a size would warrant for Nameless npcs which would Increase immersion yet require less work. At 8 times the size or more- Cities would be proper cities- there own game within a game. You could roll play a character who never leaves and still have fun.
- The Game's encounter zones would work better as you are not always constantly 5 minutes run to a hub. Meaning less level scaling would be necessary.
- It's more lore friendly, in a weird way. It's not Perfectly lore friendly, But it is morso. Things from skyrim that suffered in this reguard
----Dwemer pressence in skyrim. There's two cities. Yet the size of blackreach and how far it expands indicates a massive dwemer pressence in skyrim.
----Someone said that dwemer technology would be remade due to the ammount of people working on it and sheer amount of interest. This is [censored], but i can see where they got the misconception. Calcemero is One of the only people in skyrim who cares and he's more of an archaeologist. Most nords would scared of dwemer.
---- Again, Iv met more Criminals and monsters in skyrim than i have met people.