I often find questions on SO that would clearly be a better fit on Database Administrators, where I am a moderator. My vote to migrate from SO to my own site is considered equal to anyone with generic VtC privileges. It is not difficult to collude, and this has happened multiple times (both me getting others to help migrate a question, and others enlisting my help), but it shouldn't be necessary and just slows down the inevitable.
As a moderator of the destination site, it is curious that my vote is not binding, and I am wondering if it is possible to make it so, as long as:
The moderator of the secondary site has earned, at minimum, VtC privileges on the source site. Or, to minimize the potential for a large number of mods from having this ability, perhaps even trusted user (20K) on the source site. This will drastically limit the number of moderators of smaller sites who can take questions from SO; it will also limit the ability of SO moderators to take from the smaller sites. On our site, I don't think we have many SO moderators who have VtC privileges (I could find out with a lot more manual research); we certainly don't have any trusted users that are moderators on any other site.
There is already an established migration path from the source to the destination. As of November 6, 2013, this includes the following sites for Stack Overflow: meta.SO, SuperUser, dba.SE, TeX, and SharePoint. For most other sites the list is far, far smaller - for example on dba.SE we can only migrate questions to our own meta and to SO. And of course the smaller sites individually have a small number of moderators. So this really affects a much smaller portion of the moderators than pointed out in a concern below (300+).
Optionally, there has to already be some number of VtC votes (of any type), perhaps 2, for a moderator to place a binding vote. This will prevent a moderator from making unilateral decisions about questions without there being some minimal evidence from the community that, in some way, the question doesn't belong on the current site. However, this is not a hard requirement for me. I am willing to live with it if it is necessary for the feature request to pass.
With linked accounts it should be technically feasible to see that I am a moderator on the destination site, and in that case only (in addition to the above requirements), forego the need to collect more VtC actions before migration.
For clarification, this feature change is probably only necessary on SO, but if that makes it more difficult to implement, having the rules everywhere - given the above restrictions - shouldn't be harmful, because the number of use cases where it would affect a smaller site in any way will be quite low.