An active skill list sounds interesting, but it's hard for me to see a way for it to be both useful and balanced. I suppose that the best way would be that you can only swap skills while out of combat.
A concern I have is to better balance the skill distribution. It's silly that some trees have only 5 or 6 Novice skills (but you can only learn 6), whereas some trees have 7 skills but you can only learn 4.
I also think that this might be a better distribution table:
N / A / M
=========
3 / 0 / 0
5 / 2 / 0
6 / 4 / 1
7 / 5 / 2
8 / 6 / 3
More skills can and should be added to the game.
