This would be very useful feature for many custom workflows, where particular steps should be taken by members of specific groups. And it doesn't look like much development would be needed here. Anyone at Atlassian care to look at this?

We have implemented the following solution to your requirement by using the JJUPIN plugin and the User Group Picker

First of all we also disable the Assign Issue right for most of the users so they do not assign the issues otherwise than by transition screen.

The JJUPIN plugin introduces a Simple Issue Language meant to simplify your special processing in conditions, validators or post-functions.

User Group Picker permits the filtering of the users to a group or role.
You may create a custom field named "Assign to Tester" (E.g. with ID 10123), that is restricted to a specific group (or role), let's say it is called "Testers".
On the transition screen add the CF .

On the post-function assign the issue to the selected user

  // you may access a customfield by customfield_nnnnn, by name or by alias
  assingee = customfield_10123;

You may also want to write a validator in order to make sure that the CF "Assign to Tester" is set.

Here is how you create a condition, validator or post-function: http://confluence.kepler-rominfo.com/display/JJUP20/Writing+Validators%2C+Postfunctions+and+Conditions

We are quite surprised that this functionality is not provided given that you already have 'Assignable User' permission at the project level. You should also be able to provide capability to set assignable users at each workflow transition. This is a feature that we really need.

I have several customers who really, rally need this.

Pretty fundamental thing to have.

This is a big, BIG, BIG, BIG request I have needed since day one. More than a year ago. I reported this in JRA-6053, which has been resolved as a duplicate of a larger issue, JRA-6381. Please add your vote!