Since we're talking about takeout, it's always a good idea to export your Gmail inbox once a year, encrypt it with GPG (or something similar) and store it offline somewhere on a drive.
I use a google script with time trigger and filters to download each message (30 days or more older, so that I have time to delete unwanted), as .eml files too, along with your suggested mox files.
https://github.com/jay0lee/got-your-back