I think we have GU strategies already, but I think EternaBot distributes a little too much GU and wrongly placed.
For easy labs:
Give +3 if GU% is 0-5%.
Give +1 if GU is 6-10%.
Give 0 and start penalize for higher GU percentage.
For hard labs, open ended labs included:
Double the percentage allowed, per reward.
Background article: EternaBot report