Once a user has discovered he has posted a question on the wrong site, it seems to me the usual solution that they arrive at is to simply cross-post it on the second site.
Even established users do this (I've just been discussing it with a 15k rep SO user).
Rather then having to:
- flag for a moderator and explain you want it migrating
- vote to close it and choose a new target (along with 4 other users?)
- cross-post and delete the original
would it not be better to include a
move) link under the question, obviously only visible to the OP, and take them directly to the list of migration targets?