There is a mod Nomadic Tents that allows you to set up various yurts and similar structures. These can be larger on the inside than the outside. They function by the door essentially being a portal that teleports you to the "tent" dimension where the interiors actually reside.

The tents are likely not somewhere the player will be spending a whole lot of time (probably grabbing some items, going to sleep, etc.) so frequent loading transitions are very jarring. If something similar could be done with the tent doors as with the nether portals that would be amazing.