I do not know if this is feasible, as I do not know the current design of meta sites. This also might have been implemented already, for all I know.
I think that without linking to SO as the ultimate source of meta information, questions with certain tags should be displayed indiscriminately across all meta sites, and belong to none in particular. These questions would be the questions which apply to the entire SE site network, but not a particular site in general. Questions such as general etiquette, feature requests, anything tagged with 'stackexchange' or 'stack-exchange', etc. should be spread across all meta sites. One way to do this is to keep the question on the meta site it was originally posted in but include it in searches across any meta site. The main reason to do this would be to try and reduce how often redundant questions are asked. To that effect, the questions could be indexed only in the 'similar questions' section when you ask a new question. However, I think that it wouldn't be very hard at that point to include it in searches as well. The only alternative method I can think of would be to create a new site-wide meta questions site, which would be infinitely more cumbersome to the developers and the moderators who must migrate the questions.
Overall, I don't like posting duplicate questions, even if they are duplicates of meta questions from other sites. I think it would be nice if all these questions with certain qualified tags were either made site-wide and inspecific to any site or at least indexed in all searches and included in the "similar questions" category (when asking a question). Wouldn't it be ironic if somebody found a duplicate of this question from another meta site? :)