<p>The only problem that I can see is that this won't work without your addition. And even between the existing Stack Exchange trilogy sites, I feel you need that "accept the question" component. For example, a lot of people vote to move questions about servers to ServerFault from StackOverflow, but ServerFault doesn't like to support individual desktop installations of software, which is what a lot of the questions on SO are.</p>

<p>So the best thing, in my opinion, would just be a general "off-topic" pool of questions. Someplace visible to high rep users and/or mods on every stack exchange. If they feel it belongs on theirs, they can cast an "accept" vote. Once it gets high enough (5 votes to accept to a particular site, perhaps), it gets moved. Questions can also vote to get deleted if they really don't belong anywhere. And also, stats can be collected to see if two StackExchanges are regularly voting to accept the same questions so that their boundaries can be better defined.</p>
