This can be certainly evaluated, it will very probably require libvirt changes as well.
So it looks like that RBD is supported in RHEL. Anyway, it would be nice to list only the storage pools that are known to be present but this needs to be somehow reported by libvirt because we don't want to have downstream-only patches. Moving out of RHEL-7.6 since this will need additional work in libvirt.
Moving to upstream, this will require support from libvirt to report which storage drivers are supported and it's a minor issue to backport it into RHEL-7.
There is the pool-capabilities API nowadays which could be used to report supported pool and vol types. I would take a patch to support using it, but implementing support for it is not a priority for upstream nowadays. So I'm closing this as DEFERRED