I am the author of the Firefox Environment Backup Extension (FEBE). Some years ago, I wrote a version of the extension for Thunderbird (Thunderbird Environment Backup Extension or TEBE). Unfortunately, I was never able to devote the time required to get it out of beta. I estimate there are approximately 50 to 60 thousand current users based on the TEBE homepage visit stats, but I may be off a few thousand.
A little over two years ago, another developer (Gary, spaceShot9) took over TEBE and got it up to the then current AMO standards. But now it really needs to be rewritten again to adhere to the more stringent standards (i.e., wrapping all functions into a single object, replacing deprecated xpcomm calls, etc.) Gary has seemed to have gone MIA and he has not posted in the TEBE forum or responded to my emails for quite some time. I'm sure he has probably gone on to other projects or is otherwise too busy, but I do commend him for tackling the project initially.
I believe there is a real need for a robust backup application for Thunderbird. One that can backup/restore not just the full Tb profile, but individual parts such as address books, filters, messages, installed add-ons, etc.
This project does not necessarily require a single developer to adopt. Perhaps a team of developers could do it. It could even be a completely open source project hosted on GitHub or a similar venue.
TEBE does work now with the latest version of Tb (v24.5.0). I have been using it daily for years and have had no problems. There have been no recent bugs reported in the TEBE forum, so the code is stable.