Can any live gmail backup tool import a takeout file and resume from there?

I haven't always been as good about backing up my gmail as I should. Sure, I've got partial archives on the various IMAP clients I've used, and I've tried a few of the backup tools. But they're all in different formats and have a different set of my emails.

I'd like to get a unified single backup that I keep up-to-date.

What I'd really like to do is download a takeout archive, import it into a backup tool, and resume updating the backup tool's database incrementally from there, perhaps as a cron task.

Can anyone recommend a backup tool that can be seeded this way?