Afforess
The White Wizard
Okay, I've got it working. I need to fine tine it a bit, but the follow command does let you select a unit, and the unit follows correctly. Smeagolheart is working on a button for me. I should have it up at the very latest, Saturday.
I can already see Automated Carrier Groups making their way to my enemies shores
Or Horse Archer outriders defending their Settler charge 
Actually though, I'm kinda surprised that you didn't think of the popup yourself...