You can create buttons which always copy in unattended mode using a command like Copy UNATTENDED=yes
Allowing operations to start with minimized progress bars via something similar to (but not identical to) @runmode:hide might make sense.
Regarding resuming and automatic retrying, except for the FTP/SSH functionality (which do things differently), Opus is designed around the assumption that your devices are generally reliable. What kind of thing are you doing where it is so slow and fails so frequently that you want automated retries/resumes? How reliably could you resume such a failure? (e.g. if it isn't clear how much of the file was transferred without padding or corruption, resume may not be a good idea) Would it make sense to use another protocol to transfer that data, instead? (e.g. FTP itself, or BitTorrent or similar. There are much better methods than standard file copy if you need to transfer large files across a a slow and unreliable network.)
Separate threads, please. There are already too many different ideas in this thread to be able to keep track of and talk about all of them in detail.