Have you ever consider to integrate a FileSystem inside MCUBOOT ?

[Gioelinho]

Have you ever consider to integrate a FileSystem inside MCUBOOT like LFS, EmFile or something else?

This could help you to save old/new firmware or organize it in folders.

[de-nordic]

Your application should be ding that and loading desired image to secondary slot and marking it for next boot.
Adding support for filesystems in MCUboot would bring a lot of problems and security issues.