The project is working. The file system works in the three modes which can be controlled with the switch.

The sources can be found on GitHub:

https://github.com/elbojvv/fat32prfs

https://github.com/elbojvv/prfsswitch

Proftpd and samba are working. Only Windows get really confused when switching the modes while working on the files through samba. But this was also not the intended use. Also, if you delete a backup file through samba, it seems to be deleted, but after a refresh the file is back.