Ironically, I'm back at square one - and it isn't a bad thing.
What I mean to say is, I'm using the original movement setup (physbox leg pieces constrained to a tracktrain), only this time it WORKS. Instead of making the axles in the legs as the train, I made a separate brush that is textured with nodraw and is very small. Also, I replaced the very complex axle connection that joined the leg to my test cockpit, which was one of the reasons it failed at the beginning, with the phys_ballsocket that [VDC] Rad Brad suggested, and the results are much better.
Now, the only problem - other than setting up a true-to-life movement path - is to get the constraints to stop fighting each other. I know this will require constraint systems, but I truly don't understand how they work (Hammer's description is clear, but I am having trouble fitting it in my project's context). Mind you, I'm going to try to make it work right now, but I don't think I'll get great results. Anyone have a "for Dummies" explanation?
P.S. once I have this problem worked out, I
WILL upload a sample map so you can see all of your intellectual contributions working together to power the leg