Why not have the Crystal Trade Slider be able to go both ways?
Im sure there are numerous members here and on Kongregate that could use this feature.
Hows about when you "Forget a Skill"( 20 Gold) that maybe for a additional 5 Gold or 1-2 Gold Per Level that you get to keep the Level your Skill is currently at.
I mean we have already have worked to get to this level with Upgrade Cards seems reasonable to at the least to retain the current level.
If you so desired to retain the same level then a option to do so with some extra Gold would be a more then welcomed..
This a is another feature that would go over well in TW and Kongregate as well....