I think something like Arch or Subversion, with an accompanying Wiki for developers and users to converse (and converge) is a good idea.
I'm starting to doubt the whole idea, how nice it may be: Are there any other active patch makers out there except us? If not, then is it worth all the trouble? For me it's very easy to keep my https patch in sync with your tabs+frames patch, I'll just sync with CVS when you have a new version, and then attach your version number to the filename, so that it's clear which patches are compatible with eachother. Of course doing the same with other patches won't be as easy, because they may conflict, something that's unlikely with the https patch and frames+tabs patch.
BTW, I also double as a software evaluator for the GNU project (Even though I've not done many evaluations lately for lack of time), and would be more than happy to get Dillo listed as a GNU project.
What are the advantages of being a GNU project? Greetings, Indan