So for my work, I needed yet another addition to the whole slew of options that mylvmbackup already has. This time, I added a keep_mount option. The dpatch can be found here. The package with this patch and my previous work on mylvmbackup (which added support for a defaults_file instead of plaintext username/password credentials in the mylvmbackup.conf) can be found in Kumina's Debian repository.
WARNING: These two patches are my first steps into the wonderous world of Perl. I only checked if they did what I wanted them to do, not if it still worked as required without this extra code. Your mileage may vary, so be sure to test!
Also, if you use this, please let me know! I'd appreciate it.