I don’t think you can do any better than to study how that rig is assembled and implemented – it’s really a very good design for general character animation. I haven’t yet pulled it apart myself but have done a number of sequences using it, and it rocks!
But one of its characteristics that I like a great deal is that it is not highly “automated,” at least not in terms of how it’s used. It has handles for all the principle bones and/or controls that are practically needed, but doesn’t seem to have a lot of constrained interactions other than the usual like foot roll. This puts more on the animator to set all the poses just so, but for me, that’s a better approach, since it doesn’t pre-suppose a particular way for the bones to act, the way constraints must in order to work well.
When building the control system for the Othello face rig I ran into the problem of how much automation is a good thing, and it took quite a bit of fussing to get the control system to leave room for manual tweaks after the control mechanisms had been set. But that’s really important in designing constraints imo, because there will always be a time when constraints aren’t doing things quite right, and the animator has to step in and tweak it just so.