@StackSounds - the whole experience is in breaking through particular areas (rubble and similar), smashing through vents, or otherwise finding ways to get through the area to loot the goodies. Mods like Minify Everything basically trivialise the intended experience since you can just uninstall blockers like big heavy doors instead of taking the time to destroy them. Not having HP on walls makes them invincible and means you can't just break them down to bypass the intended routes.

Note that this mostly applies to the various Z-levels underground, the surface areas tend to be more open and easily explorable.

@StockSounds
1. Not so much
2. If something cannot be broken, it can be disassembled.
3. No

I haven't quite gotten to playing Ancient Urban Ruins, are a lot of things just not breakable? Is there some areas that are unbreakable for a reason, or is breaking through walls just "not the intended experience"? I haven't tried it before but that does sound like a good change.
It doesn't add hit points to staircases, right?