Apologies - this is probably off-topic, or at least veering off in that
direction. Also apologies if this has been addressed previously and I've
missed it - if so, I'd appreciate it if someone would point me at the
discussion.

Given the successful removal of systemd from debian, and the consequent
existence of devuan - it seemed to me that the obvious next step would
be to take an RPM-based distro (maybe centos) and attempt to apply
equivalent procedures to it.

But - at least based on extensive google searches - I can't find any
evidence that this has even been considered, let alone tried.

If it had been tried and found to be impossible, impractical or
pointless, and if this had been reported, that would seem reasonable.
But the lack of any mention or discussion of it whatsoever seems
strange.