It’s strange not to see other comments, especially from MT team. This question has been asked many times and every time a script has been suggested as a solution:
http://forum.mikrotik.com/t/routing-with-dynamic-gateway/36494/1
http://forum.mikrotik.com/t/how-to-route-on-dynamic-gateway/12184/1
http://forum.mikrotik.com/t/ecmp-on-dynamic-interfaces/4456/1
http://forum.mikrotik.com/t/changed-policy-routing-with-dynamic-ips/1787/1
I believe my solution is simple to use, easy to implement and completely solves the problem of policy routing via dynamic gateway. Would it be correct if I e-mail this feature request to support@?