should've been done along time ago.
While the OP asks for stairs/ramps/ and climbable slabs, most of which don't seem likely, The discussion once again turned to a more practical object: Ladders.
I also added the idea of waist high fences as well. Now what we have the LOD system this should be very possible.
Feedback:
Fence should be possible as LoD model,
We may want three materials:
Glass, Metal, Wood.
However Metal is the preferred to be the first one to be implemented.
(Its also wished to be in the middle not at the border of the block.)
A "Corner pipe" also could help to get around with slabs around corners.
Also in regards to the LoD system, pretty sure the community would rejoice if any kind of LoD chair/bench is added. The makeshift chairs look bad. Even Minecraft can do it better. (Stair block and two fences). I think it's been avoided until chairs with certain usefu integrated functions could be added. But I'd love just to have a prop or new generic LoD detailing blocks that could be be combined with other blocks to create something that somewhat resembles a chair.