Looks exactly like what Mountain Duck from https://mountainduck.io/ already does.

Although it requires a prior additional authentication step with OAuth 2.0. Cyberduck just added interoperability for in version 5.0.1.

Tested it Cyberduck from Belgium.

Upload speed: 1.4MB/s. Close to my maximum of 1.6MB/s.

Download speed: 1.3MB/s. Far from my maximum of 15MB/s.

This could be good for NAS backups.

Considering the agreement jankey linked to above says bandwidth is limited to 10Mbit/s (1.25MByte/s) you're getting "bonus" throughput.

I agree, offsite back up of local storage is a good use case.