1) I am talking about having the ST-E3-RT in the camera's hot shoe, controlling the off-camera 600EX-RT flashes, and at the same time the FlexTT5 via the PC port on the same camera controlling the Einstein/MC2. So, exactly like your CyberCommander + Canon scenario, except replace CyberCommander triggering for the Einstein(s) with PocketWizard triggering for the Einstein(s). Any idea if that would work?
I just tried it, and I couldn't get it to work.
I put the ST-E3-RT in the hot shoe, and connected the FlexTT5/AC3 combo via the cable I got with my Einsteins. The "Test" button on the FlexTT5 fires the Einstein, but the Einstein doesn't fire when I take a photo. I tried connecting the cable to the P1 and then the P2 ports on the FlexTT5, but it doesn't work.
The FlexTT5 quick user's guide doesn't even mention the P2 port, the online Wiki manual is useless for searching for such things, and I've been waiting quite a while for the "generate a PDF" link to produce something.
I'll investigate more later this evening.