Sure you can!! Stairs and ladders are full compatible with 2.5D levels

Pay attention to:
setentityvar(self, "width", X); // width
set the right width
For stairs you can set additional params like:
•setentityvar(self,"subject_to_base",value): 0,1 --> the enity cant stay under the stair
•setentityvar(self,"subject_to_depth",value): 0,1,2 --> USE IT TO BLOCK THE ENTITY. 0 means that you can walk in depth. 2 is for blockade totally in the middle and 1 to block only when the player is stopped. ### I like subject_to_depth to 1 ###
•setentityvar(self,"subject_to_edges",value): 0,1 --> blockade on edges
set these params all to 0!!
ps. yes you need to copy all files. this is an "all in one" script for speed-up improvements and for interaction between the new features!