are we able to have RDS with much faster CPU and RAM and support Ceph?
This would be game changer and distruptive.
Personally, I would not run Ceph on any device with such a large number of flash disks.
If it was 3.5" spinners, yes. For all-flash you should probably just use NVMe/TCP.
Speaking as someone who has run multi petabyte Ceph installs…