JRA-2737 was misunderstood and has not been resolved. What Nick Minutello wanted was a dropdown or picker with the users from ONE group or project role. Maybe more than one group but definitely (a) not all users and (b) not from all groups.
Our actual problem is the migration of solutions to our servers. Not all people have the rights to migrate solutions to the next test stage or even the production system. So it would be nice to be able to assign issues to the corresponding "migrator" for the specific server. Having manually editable lists here is not a really good solution. Assigning to a group is no solution either because no mail is issued.