what do you think about the idea of porting the skill system directly into the game world instead open a boring menu screen where you learn new skills by making a click. I mean a skill menu is breaking the flow and rip you always out of the immersion. When Henry would learn new skills by talking to other NPCs who can train him via a dialog where they say to Henry what he has to do to become better. For example for faster riding a NPC could give Henry some hints how he has to sit on the horse to become faster. The game would not break by a menu and all that would give a more realistic feeling, making the world more organic like something that really exists. Not just a boring generic skill tree!
Look how great this works in Gothic 1 & 2. Please learn from it.