Is it possible to use an LTM Policy for sending 301 redirects?

Your should create only one LTM Policy that will contains only one Rule.

The Variable Redirect will contains the actual url to be redirected.

The iRule will read the variable Redirect and will redirect to that URL

In my case I redirect to HTTPS. You create a Virtual Server, and Assign the Policy and the iRule. Policy is read first and then the iRule will contains a value for the Redirect Variable.