Questions can be moved to any SE site but only by moderators.
I think the best thing to do in this scenario is to flag the question for Moderator attention and mark it as "other". Then add a comment in your flag as to where you think it should be migrated to.
Adding even more migration paths to this existing close list would clutter the UI. The idea is to show the most frequent migration paths so the users to can migrate most questions.
Moderators should only need to intervene in exceptional circumstances.
