[GeeTwo]

It looks pretty good as a concept, but I've got to wonder:
1) As I look at this, this is a system to constrain an elevator, but makes no attempt to actually extend/retract it. Am I missing something?
2) I found it strange on the "Stepped Roller Kit Render" that there were two separate axles on the single (presumably moving) arm; wouldn't it be simpler to have a single (slightly longer) axle on each side with two of the stepped pulleys? For that matter, wouldn't it be simpler (and tighter, and easier for teams to "get right") to have a single (much longer) axle for those connected to the "stationary" pair? Even if it were not as stackable as your general design, having this as a simplification would be a great help to teams with more meager machining resources.