I’m not certain the Verify result is entirely equivalent when run later. You might miss some problems that could have been cleaned up at start of next backup, except you didn’t. Any damage may become worse.
I think you’ll see this get especially active when a backup is interrupted before it runs to a clean ending.
Manual compact should be fine, I think.
The challenge also shows up in the Target URL used by command line and GUI internally. Some syntax would have to be invented to say have-this-wrap-that. GUI could use same plan. It still takes much work.
Branding and OEM customization talks about custom backend configuration but also says the following:
Since the backends are loaded dynamically this would simply require that the unwanted backend files are deleted before repacking and signing.
I don’t think they’re as easily added as removed. You can look at how Rclone backend was added here.
It’d be interesting to know what (if anything) has this use case covered (and with what usage limitations).
Glad to help.