I noticed the Lightning door didn't seem to work, instead units could just walk through it like a magic wall.
Turns out, doors placed in the 'Content' part of a map block (where the door was placed on the map) don't actually work. So I just moved it to the "West" wall part and it works fine.
Other fixes include: LOF fixes (even though the engine specifically fixes the Lightning walls) but also including LOF fixes for the stairs, which had a few gaps in it.
I also tried my hand at restoring the Avenger doors. I modified the tileset to move them to the north side of the tile so that they match up with where the engine puts North doors. Therefore the doors behave and animate just like you'd expect.
Here's the tileset, if you want to see how I did it
The only oddity is with lighting, but it's minor:
I suppose I could just replace them with flat doors to solve this.
Also, for both, I made some tweaks to get the minimap images of the Lightning and the Avenger looking proper (except for shadows, but nothing I can do about that). I did this by swapping the minimap graphics for the corner floor-tiles and the diagonal walls, since the walls' minimap graphics will draw over the floor tiles.
Before:
After:
