Just a list of things to research:

Floor Shader:
- Allow culling (double-sided tiles)
- Can we get access to the ceiling side of the floor edge?

Floor Edge Shader:
- Is it possible to select the floor edge in-game?
- Is it possible to have the floor edge match the floor tile?

Wall Shader:
- Can a zero-thickness wall take an alpha channel?
- Can we set the verticalSpan for deck walls to floorToFloor from floorToFloorBasedCeiling, without losing the shader which allows an alpha channel?
- Allow animations (http://www.modthesims.info/showthread.php?t=460702).