I haven't heard of a way.
Would something like Mail Tags help?
I tried the workaround you mentioned and found it was just too much effort for the minimal payoff.
Personally I use the "Support" method the DAC coaches suggest where you define the next action that points you to a folder labeled "Action Support" or "Waiting For Support". The other method is where you use the email itself as the reminder in "Action" or "Waiting For". The key I've found is you have to pick one method instead a blend of the two.
My next action looks like this (in OmniFocus):
"Read interest rate article
See Action Support email from Wells Fargo on 04-22"
(the second line is in the notes section but it would work in any system including a paper planner)
This method points me to both personal (Apple Mail) and work (Outlook) content. I've started using TextExpander to get things like Snase = See Action Support Email
Wow ... long answer to a simple question.
How did you capture that thought?