DA will always want to set up DNS.
It's not going to be easy because DA updates /etc/named.conf and creates sone files in /var/named/.
You'd have to use symbolic links so DA and BIND will look in different physical locations for /var/named, and you'd have to set the startup script for BIND so it'd start with a different named.conf file. Then you'd have to create a script to read the named.conf file DA creates and create slave references to add to your custom config file.
Run the script on a cronjob, or after each domain is created.
Then of course you'd be responsible for updating your own DNS server(s) whenever DA creates/deletes a domain, or changes it's IP#.
Much easier to use your nameserver as the slave, though you might still want to call it ns1.
That's what we do.
Jeff