Before I make this suggestion, I'm going to lay out some guidelines for what should and should not be migrated between sites. The method for migration I'm about to suggest only makes sense if we can all agree to the same set of guidelines for migration, I think. Feel free to disagree with this guidelines, but if you are going to do so, please clarify that you disagree with part of the guidelines in an answer.
- A post should only be migrated if it is off-topic on the source site.
- A post should only be migrated if it is on-topic on the destination site.
- A post should not be migrated if, for any reason, it would be closed on the destination site.
- Being on-topic for destination site does not automatically make a question off-topic for source site--there is overlap between the sites.
- If the question has answers, those answers must also be a good fit for the destination site.
With these guidelines in mind, can we agree with a few points?
- Members of the destination site are not going to be the best judges of what is off-topic on the source site.
- Members of the source site are not going to be the best judges of what is on-topic on the source site (and whether or not, for any reason, it'd be closed on the source site).
Obviously, some people will be members of both sites
So, with that in mind, here is my suggestion.
Completely remove the migration out of the closing menu.
The following option should be removed from the "Closing" question menu:
This question belongs on another site in the Stack Exchange network
I know that going through this menu option will result in the question actually being migrated as opposed to closed, however, the fact that this option exists within the close menu seems to suggest to users that this is a close reason. It's not a close reason, however, it's a migration option.
That users get the idea that this is a close reason means that the custom close reason is frequently used with comments like this...
I'm voting to close this question because it belongs on [insert destination site here].
Which isn't an acceptable close reason. It makes no recommendation to the user on how to make their question suitable for source site. In fact, it doesn't even imply that the question is off-topic for source site. And questions which are not off-topic for source site should not be migrated (point 1). They certainly shouldn't be closed (except possibly as a duplicate).
Add a "Nominate for Migration" flag.
First, calm down. This flag won't be handled by moderators (definitely not moderators on the source site).
Anyone can raise a "Nominate for Migration" flag on any question at any time. Moreover, they can nominate a question for migration to any destination site (from a UI end, think of a searchable box like on SEDE).
While the question remains open on the source site, the flag is entirely meaningless. A question on-topic on source-site is not a candidate for migration.
At any point in time when a question meets the following two criteria:
- Nominated for migration via a flag
- Closed on the source site
The question will then show up in the review queue for any/all sites to which is was nominated for migration.
Add a "Suggested Migrations" to the Review Queue screen.
Questions which have been nominated for migration to destination-site and closed on source-site will appear in this "Suggested Migrations" queue. Users with the appropriate reputation level (doesn't matter what it is, but all of the moderation tools are gated behind reputation) will be able to see these questions.
Reviewers will have the following options:
- Approve Migration
- Reject Migration
Skip just skips the question, of course, taking no action.
Edit gives the reviewer a chance to edit the question into an on-topic question for destination-site. This option may have to apply edits contigent only upon the migration being approved.
Approve Migration gives the question a vote toward being migrated. With enough "Approve" votes (presumably five), the question is then migrated and appears on the destination-site as a regular question.
Reject Migration gives the question a vote against being migrated. With enough "Reject" votes (presumably five), the question is removed from this destination-site's review queue and migration is denied. The question will never appear on destination-site.
Obviously, moderators on destination-site could have binding votes so their single-vote automatically approves or rejects the migration.