(Not sure whether this is the best place to post this -- if not feel free to move.)
I've written an interactive sync programme many years ago (and still maintain it). I use this for all local syncs including to/from SMB locations. This works in two steps: the first is a CLI that collects all file information for the two directories to be synced and then does the heavy lifting of date-time/size/checksum comparing and deciding what to sync where. When done, it dumps a list of to-be-synced filenames, their datestamps and sizes and a tentative idea of the sync direction into a file. That in turn is read by the second part, a simple GTK app that shows all files (and their information) in a big listbox and allows the user to either ignore files, to delete them (both, left, right) or to change the sync direction on a per-file basis (or simply to sync the datestamp to either direction). Once the user's finished with those selections, the app then ignores/copies/deletes as requested (or creates a shell script to do the job).
Now I'd like to use that very same app for rclone syncing to remote hosts. The easiest way would be to use rclone's mount feature; I'd expect this'll run as usual as my sync app just needs two mounted directories and doesn't care about the backends. However, I am not sure whether this is the best way forward (I am a stickler for reliability rather than speed when it comes to backups).
Another strategy would be to "somehow" get a listing from rclone that shows the required bits of information, ie filename, the two datestamps and filesizes and the proposed sync direction for each file to be synced. I've seen that a dry-run bisync will already provide some of that information (names and direction) but apparently not all. So how about adding an option to bisync (or another suitable rclone command) that just creates such a list but never actually syncs anything? I could then save this to a file, massage it a little and hand it to part 2 of my sync app to make my manual adjustments. The app in turn would then either generate a shell script for rclone with all the required copy/delete/set datestamp commands or perform those commands directly by calling rclone.
The devil is, as ever, in the detail, but I think such a list could be a good thing not only for my use case. I am in no hurry at all, just want to throw this into the air for consideration.