How to ensure that TFS clients has the latest version of a custom check in policy installed?

Question

We implemented a custom check in policy, and selected it for one of our TFS project. If a TFS client does not have the policy installed, TFS will show an error message with

Answer 1

You could add policy version number to the end of policy name and introduce the updated version as a new policy.
This solution comes with a little management overhead but makes sure the you get the error with every new policy version.

Answer 2

Finally I decided to use the workaround originally suggested:

"One possible workaround could be to checkin the latest version number as a file to a project which can be accessed by anyone. The check in policy itself would read that file, compare the version with it's own version and generate a PolicyFailure if the version does not match."

Works well.