Currently when using the Planning Board to assign issues, all users that have the assign-to permission appear. If the number is larger than 75 users, this feature is switched off.

In many organizations engineers "can work" in most projects, although they are "likely to work" in just one, maybe two. Therefore for any project the number of users with the assign-to permissions will be large. However the number of user which are "likely candidates" for the assignment will be far smaller. If it was possible to specify an additional user group (I.e. the "project team") to filter the assignable users in the Assignee Board, then this problem would be resolved.

See GHS-1246 for some background discussion.