so now that we agree on that you dont have to exclusively use tube levels to do storytelling
Discrete areas dont change the basics, its just a different kind of door between rooms.
Skyrim has a lot of those and its very open world anyway
And just because ME did it that way until now doesnt mean that they have to do it that way again.
Embed the big main story dungeons into the world like everything else and dont just make every single area single use.
Some areas can be single use, or single time interesting
But not the largest part of the damn world, so much time in level design wasted because its just a run-through area.
And for encounter design and cover gameplay:
Design the encounters that there is cover in all directions that the player could use to get there (y'know, like proper para-/military post design) and/or give the player and NPC's the ability to create and destroy cover objects. (Tech/biotic barriers, environmental changes with grenades or biotic kinetic pulses, blah).
They also already showed
"freerange" encounters with that desert outpost which was seemingly in the middle of nowhere and surrounded by mostly flat terrain.
So the encounter design cant be that large of a problem
when bioware with decades of game building does it in the fourth
installment of a game series