Wow -- Thank you for your time on this Andrew! I will investigate the use of Content Controls. I was vaguely aware of them, but had not used them because I was afraid they would be too cumbersome to insert every time I add a bit of narrative to my boilerplate text.

It would be nice if they could be added "on the fly" while typing. For example if I type "Something FirstName something," and the "FirstName" instantly became the mapped control of that type. I did a bit of google searching in the past and didn't see a way to do that. As I'm typing this however, it occurs to me that maybe the CCs could be saved as QuickParts, and inserted by typing the name...

I shall experiment!

And I agree -- This is way cleaner than what I had going with the customproperties!