Doug,
I had a look at doing something like this a couple of years ago. There are a number of things on Windows that are either at least different or significantly harder on Mac so there are potentially a lot of new problems to solve. I haven't looked at your code but for example
a. there is no reliable documentation for Mac Office VBA or Mac Office Applescript. Many things are the same, some things are missing or different, and some things look the same but are different or behave differently.
b. it is not even possible to look at the Word object documentation via the Mac Word 2016 VBA editor, because that option does not exist. So although so far I have found that using the equivalent feature in Mac Word 2011 gives the right informaiton, only experiment can verify that new features have not been added and that behaviour remains the same.
c. you can only really control Mac Outlook via Applescript or by using a Javascript Addin (as mentioned by Jim Gordon).
d. Even doing a one-merge-at-a-time mailmerge has to be done differently because the object model on Mac Word is like an older version of the Windows one
e. AFAIK the only reasonably simple way to access Excel data is via the object model (there is no ADO, DAO, OLE DB and using ODBC requires a commercial third-party add-on). IME controlling Excel reliably via Automation is not as easy on Mac.
I'm not saying it can't be done. What I'm saying is that there's a lot to discover, deal with, and make robust. And then there's the support...
But having a bunch of VBA code as a starting point would certainly make a huge difference, and I would certainly be willing to have a crack at a re-working if you are willing to share the code.