Price sets give you the tremendously useful ability to add a price field in which a user can enter an arbitrary amount. This is done by choosing an Text/Numeric field type, setting its value to '1' and NOT ticking 'Display amount'.
However, we want to use this to create an arbitrary-sized discount for admin users, and Civi doesn't seem to allow negative numbers in this field.
It's perfectly possible to make discounts of fixed amounts in a price set - the screen shot shows that our fixed discount has been included in the price calculation.
What would need to happen so that this 'arbitary amount' field can accept negative amounts?
Thanks for your help!
Drupal 7.43, Civi 4.6.17