I think you can probably create a decent gameplay loop based on the pre-established foundations. For example:
1) Find a launch point or a subterranean entrance within a region that helps Link get to a sky island. Create some sort of mini challenge there, similar to shrines, that once completed, releases a lock for the main dungeon.
2) Once all locks have been released, Link can access the launch point that takes him to the region’s dungeon.
3) Region dungeon is long-form puzzle and combat content that limits usual skill set, grants some element crucial to the main quest.
As there are eight regions to Breath of the Wild’s Hyrule (one being Central Hyrule, which could have Hyrule Castle as its dungeon) and seven years shown in the etchings from the promotional material, one might assume that finding a region’s corresponding dungeon would require scouring its topography for locks/keys/what-have-you. Now, the developers could scale the number of these locks back in comparison with Breath of the Wild’s 120 shrines, and in doing so, make each lock or the corresponding dungeon more substantial as a result. However, I’m just theorycrafting here and people who complained about the Divine Beasts and the lack of traditional 3D Zelda content in BotW are stupid, so I’d be fine if we still had to find a large amount of mini puzzles.