I'll make a suggestion to this, can you just have a leader pass macro? That way you can still do the /follow focus system, all you have to do is retarget the new leader and focus on it. For a lot of us that still use a F2; /focus combo it wouldn't be that hard to use.

It would take the same modifer pass system as above, but only requre it for 1 macro, not each time you cast a spell, etc. It does require you to either set up your windows in the same place everytime or know who it switches to by memory.

This way, if you have it so the movement keys are bound as normal but not passed, you'll be able to just switch to a new 'head,' pass leader to that toon via macro, F2 to target and /focus, then all your other macros will work as normal.