That won’t work. For most registrars to accept a nameserver as a host, it has to be “registered”. Generally, it can’t point to the same IP as an existing nameserver. Also, after they did this, the actual zone file would still refer to ns(1,2,3).dreamhost.com.
One other thing that should be mentioned is that new domains on your account will not be setup with the custom nameservers by default - you’d still need to have support do this by hand.
My guess is that at some point in the future, we’ll be better setup to do this.