I actually bumped into rclone and use Amazon Drive for backups myself. I was worried they'd freak out if I stored multiple terabytes of data there, but if you haven't got any emails about nearly 50 TB of data, I guess i shouldn't be so concerned.
A silly toy project i've been working on is to be able to use Amazon Drive as a block device via something like nbd (linux) or geom (freebsd). Would let me use existing drive encryption mechanisms (no personal data scraping for advertising purposes Amazon) and have the ACD storage be a zfs pool in its own right. Basically, a virtual 'SSD' backed by a collection of chunks (1 to 8 MiB, still benchmarking...) and where TRIM deletes remotely stored chunks.