I did consider trying something like this, using AWS or Blaze.
The cost of the space for a 8-10TB library is huge.
The time it would take to populate over domestic broadband is horrible.
I have 1Gbps down, but 50Mbps up (and I get these through Coax-to-the-home) but it would takes weeks to populate the instance.
If I recall the guys at Illustrate, makers of dBPoweramp, Asset etc. tried this a number of years ago, and it did not work well and they canned it.
The price of HDDs, is such that a good backup process should provide what you need.
So I backup my NAS based library which is 10TB in RAID1 to secondary NAS units with 8TB & 2TB in RAID1 (daily rsync jobs on the directories, checked with a Windows based file based comparison tool), then take a, monthly or so, image to an off-line USB caddy with 2 6TB disks in RAID0, and an annual image to 2 4TB disks in JBOD, which are kept in fireproof boxes (these were kept at work, before Covid made remote working accepted).