Hristo, Thanks for this. I have been giving it some thought, but it is a thorny issue and I have not found a good solution (yet?).
The root of the issue is alluded to in Debian Policy[1]: sharing and diverting configuration files is at best discouraged and likely to be broken. On that basis I am minded to close this as wontfix. Does that seem reasonable? Mark [1] https://www.debian.org/doc/debian-policy/ch-files.html#sharing-configuration-files
