I'm currently designing lasercut terrain, and have been trying to get some sort of removable door to allow variation. in terrain configuration. Here is a sample of the large gate door I have, but the same style doesn't work well with smaller normal doors. is it worth trying to get normal doors to work the same way.
Personally, I absolutely love slot doors, they make it really easy to express the open-close state, they're better at staying in position than simpler stand doors so everything looks flush and 'realistic'... but practical experience with USING doors in terrain has shown me the slotted doors pay a price for that. Even if everyone using the terrain is careful the slide-in slide-out still results in more wear and tear than other door options (and when people aren't careful the chance of the paint scraping or the slot getting snapped jumps up). Its a price I'M willing to pay, so someone figuring out a slot system that works for small doors would be amazing, but that's definitely not guaranteed to be universal.
Its not too hard in theory, it's 3 layers of 1mm chipboard . Back piece is a full frame (so it looks decent when open), the second are 2 thin strips with enough space for an insert with a little extra buffer space, then the outer layer is wider that overlaps the insert. My issues are: Lots of thin strips that need gluing The buffer spacing I have in my last version is 1mm, which is a little too much. I need to redo it at 1/2mm. Or I need to increase the overlap on 3rd layer. I'm using Chipboard (heavy cardboard) that is not super rigid. I can see why terrain manufacturers don't try this. Its a little finicky, and the need to print multiple layers increases print time a lot. Also thinner material is a bit of a pain. Its far easier to just print the door on the MDF, or make it a stand.
I use styrene H-column to form the slots for my sliding doors. Spaced to suit the thickness of board I use for the building itself. (This was 5mm when I was using foamcore, I've changed to a 1/8" (US sizing because Evergreen) slot spacing with the 3mm foamed pvc I now use.)
Not sure how I'd vote here. I like doors that you can show open/closed (which matters in most of the Objective Room missions), but agree that building doors that open/close is a pain in the butt.
Check out losblock (sliding double skin) and warmill (hinged) for decent movable door solutions. The ones that actually slide out have a habit of getting beaten up or lost.