This is three requests:

1) All stair railings should have a corresponding fence.

2) All fences in the correct height range should have a corresponding fence railing.

3) Fences should automatically adjust to vertical height differences.

a) If I have a land slope, I should be able to put a fence on it, and it should follow the slope of the land.

b) If I make my own stairs out of blocks, I should be able to put a fence on them and it should look like a stair railing, because it would automatically adjust to the slope of the stairs.

We can already place fences on stairs, they just don't work as railings because they must be parallel to a horizontal surface. If fences would automatically adjust to vertical height differences, the current stair railing idea could go away, and we could just place fences for all railings, and having to maintain duplicate textures for railings and fences would be a thing of the past.