That discussion was interesting for this one, because it brings up issues such as that merging even a relatively small wiki like ten (565 content pages, 3,204 total pages) into Meta would probably take some considerable work.
We need to lower barriers to cross-project collaboration. A SUL-linked userspace and crossproject transclusion will be a good first start. We ultimately want to be in a place where merges can be done with only trivial effort.