My 2 cents...
I like the track plan, but even if you can get around to all sides, it looks like some long reaches. Not a fan of the use of casters - unless the benchwork is absolutely rock solid and the floor is perfectly smooth, trying to roll a layout of that size will cause joints to flex which leads to alignment problems, kinked track joints, loose wires, and cracked scenery.
Aside from changing the design, a couple of options are adding some access hatches (hard on the knees) or using a topside creeper (also a challenge). I'm reasonably fit and have used both of those options and regretted them. When I redesign my layout, maximum reach will be about two feet.
