Did you consider making CNAME records for the relevant _acme-challenge records? I’m sorry if you’ve already discussed this approach in the other thread. This approach can often provide a lot of flexibility in the DNS challenge validation strategy.
We don’t control the actual DNS deployment; for example, an admin that uses our software can run DNS on a single machine or on a cluster, using any of several nameserver daemons. Thus, our options in this regard are limited. We could take some steps in this direction, but that would require a substantial development effort and risk conflict with whatever DNS setup a user might have anyway.