Might I suggest a well-orchestrated letter writing campaign? Calm, intelligent letters from a variety of people might help to get the two DS movies on DVD in the form that we most want.
A good format for the letters would be to start out by praising Warners for the terrific work they've done in recent years, in terms of DVD releases, and for being one of the few studios willing to participate in online chats. From there, mention a few Warner DVDs that you've bought, or plan to buy, and express how pleased you are with these discs. Then, discuss their plans for the DS movies and suggest that they restore NODS and release the films on separate discs.
I believe that expressing our wishes for these releases in terms of wanting them to be as good as other Warners releases, i.e. reflecting Warners's high standards, would be the most effective way to convince the studio to reconsider the double-feature disc. Companies always like to know that their work is appreciated and, honestly, Warners has been doing a great job with their DVD line. Also, by referencing other titles in our letters, we will demonstrate that the fans of the DS movies have diverse tastes and that the movies appeal to a wide range of film fans.
At the very least, it will confirm to the power that be that there is interest in these movies.