Permissions associated with user defined workflow statuses

The workflow permissions work fine if the default JIRA work flow status are followed or mapped to. If say an extra couple of phases to cover testing are considered (independent of the assigned developer) then permissions are less straight forward.

Create Issue -> Assign Issue -> Issue Progressing -> Issue Fixed -> Assign Test -> Under Test -> Test Complete -> Issue Complete

From the above it is possible to build such a workflow, but it is not possible to assign permissions to the non JIRA core phases. So we would like to be ablt to assign permissions to Assign Test, Under Test and Test Complete these don't match to existing JIRA phases so we are left with unrestricted access to these phases.

It would be great if more control of the assigning of the Issue could be undertaken after it has been initially assigned.