At the beginning of the game, the player needs to select some things that will determine how many points they get to allocate, and in how many skills.
Packages should be available to make this as easy as possible - but for the person who wants to tweak - they should have low level access to make the character they want to play.
In game - skills should advance as they are used successfully. When a skill is mastered there should be options to combine mastered skills to form new skills - or a trainer or master could be sought out to gain further training.
In game - new skills must be acquired through study and/or a teacher.
In game - if skills are not practiced, they will deteriorate. Each skill needs a deterioration rate, and a re-train rate. For example - they say you never forget how to ride a bike. But - if you haven't been on one in a while, it will take a few moments before you are pedaling efficiently and with great balance. It may take even longer for you to "ride a wheelie", which could be thought of as an advanced skill of bike riding.
To that end, such a skill would require a certain percentage of upper body strength, in addition to the prerequisite balance. An old man, who has become fat and out of shape, may never again, in his life, be able to ride a wheelie, even though he once did it as a common activity in youth.
