...but not even having basics such as opening a door in the street and entering a shop without the GM loading up a new area and taking the entire party there is a huge setback and forces me to rethink the design of the areas I was going to build and the campaign I was going to run.
Why would you need to load a new area when entering a shop on the street? You can still have buildings inside an area that are fully decorated and filled out as far as I know. You don't teleport to new maps when entering buildings in D:OS or DOS:2. Taking a flight of stairs to a new level within a building will be a little awkward since in that case, I believe you will need to move the person to a different map section in the same level, but you shouldn't need to load a new level if you included the 'upstairs' section somewhere in it.
