Perhaps DreamHost support misunderstood your question. The 'Stricly Business' plan is the only plan the includes a unique IP in the plan cost, but I believe you can add unique IPs under any plan type for a cost ($3.95/month).
I am also on the level 1 plan and while I do not have a unique IP address for any of my domains, each domain does have a small Add IP link in the Manage Domains section of the panel. Clicking this link takes me to a confirmation page, so I can only assume that it works.
Do you mean pointing at real external name servers, or simple nsX.yourdomain.tld A-Records that redirect to the real DreamHost name servers?
If you are referring to real external name servers, then yes this can be done but can be problematic if your domain does not have a unique IP address.
If you just want to use nsX.yourdomain.tld name servers that redirect to nsX.dreamhost.com, then this can be done too. There have been a few recent forum threads that discuss how this is done.
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