Thank you Stefano. You can still do it if you can (if you have time). I don't expect the DNS records to be changed frequently (unless the IP of the VPS is changed). So, I don't see much advantage in "owning" them ourselves (although I agree that this would be better).
As Joost said, jathan has become a bit unresponsive recently, due to personal issues (as jathan said himself).
Joost himself refuses to do it, and I don't understand his reasons (I don't think there is a need for a backup DD, at least it is not required for adding DNS records).
If you add the DNS records, Joost can be a backup for sure (I'd be happy if he does).