Are you open to implementing quests that modify skills or enable new ones as an award?
i.e.
- reward grants a reduction to the skill point requirement of a node(s) to reach another node(s). (If node would only require 1 point before reward you could now skip over it)
- reward enables a previously unavailable branch of nodes to a skill
- reward gives you an option of an alternative null node(s) on skill tree
- reward replaces a node(s) with another node(s) variant
- reward enables placement of an additional point to a level 20 skill
- reward enables access to entirely new skill based on your class
Edit: I was looking at the kickstarter page. It does appear that with the Lost Memories element of the game that there is some feature to be implemented that will affect skills from finishing quests of different time-lines. I do look forward to seeing that aspect added.