Ugh... The 4427. I think ER, MTL, Walters, and Trainworx all made versions of this and all did only one run.
I hope Atlas update their molds a bit and cranks these out like no tomorrow. They would really component their Thrall hopper in the Trainman line.
My guess on MTL is that they are working on making walkways out of something slightly less time consuming to make.