Allow user picker custom fields to have a default setting of 'Reporter'

Allowing its default value to be set to 'Reporter', would mean that when that field appears on a particular screen, it is initially populated with the value of the 'Reporter' of the issue. Most probably that would occur on issue creation.

Possibly this is part of a larger request (which I couldn't find when I searched), which is allowing custom fields (of any type) to have default values of any other fields (stock or custom).