We have usually the same statements against more/simplified migration paths like stated in this question:
- the question is low quality and should rather be closed
- the question doesn't belong on the target site either
- the question doesn't fit target site requirements, especially tags
- the OP needs to join the target community
- there are not enough requests to establish a migration path
A very obvious solution for the first two points has already been suggested: You can only vote to migrate to sites where you also have 3k reputation. This sort of guarantees that you know it's a valuable question belonging to the target site. This will even reduce the number of bad migrations compared to now (where you can vote to migrate without much knowledge of the target site).
This requirement also enables users to solve the third point: The first one to vote for migration needs to adapt the tags to fit the target site.
The fourth point is nonsense, I think: For unexperienced users it feels much better to get a "we moved your question to the correct site" compared to a "this doesn't belong here. Go elsewhere".
Finally, there is no need for established migration paths if the migration quality can be assured in a better way. Typically, there will be a bunch of users knowing the target site better than the moderator does.
I even believe the real number of migrations is much higher than visible, because you often see migration recommendation in comments, resulting in questions being deleted and asked elsewhere without being counted.
With these prerequisites, the number of required votes can be reduced to three, because those three votes will have a better quality than the four votes before.
I see several advantages:
- Less wrong migrations
- Better quality of migrations with already adapted tags and style
- Less frustration for users who did ask in the wrong community
- Less work done twice due to questions answered in the wrong place