Allow users of subprojects to be selected in board scope

Problem to solve

You might use a project structure like this:

• Topmost
  • Sub A
  • Sub B
  • Sub C

A user is assigned to the subgroups A and B but should not be able to access C. However you'd like to create an issue board listing all issues of this user. So you will create it at the “Topmost” level. Unfortunately you are not able to select the user in the board's scope settings since he is not assigned to the Topmost group as a user.

Further details

Use case is an agency that has dozens of projects with different assignees. However everybody must have his board on the Topmost level to have a complete overview of all tasks in all projects.

Proposal

The assignee selection should list group users first but should allow for other users as well. This would be the same behavior as when filtering the board from the filter bar.