How frequently do you think restful apis move to a new version?
Typically you don't release a new version until you need to do significant changes to the entire layout of your api. In which case the old version is not even relevant. With this in mind, you would not want to promote using a new version of the api for one resource with an old version of the api for another resource.
Just thinking about it sounds dirty. Your migration strategy should include sufficient time for you to assist your clients to move to your newer versions.
Typically you don't release a new version until you need to do significant changes to the entire layout of your api. In which case the old version is not even relevant. With this in mind, you would not want to promote using a new version of the api for one resource with an old version of the api for another resource.
Just thinking about it sounds dirty. Your migration strategy should include sufficient time for you to assist your clients to move to your newer versions.