The original Runequest tabletop made use of a D100 skill based system, this would well for the computer game. The idea was you did not have "levels" or classes. As you used a skill you had a chance to make it better. (Very simplified explanation follows)
So lets say you have a 50% hit chance with your great sword. After enough use (as judged by the GM) you got to roll to see if you "skilled up". You would roll a D100 and if you rolled above your skill level you skilled up. This means lower levels where easier than higher levels to skill up and as you approached 100% your chances to level up slowed down drastically. In fact if I recall at 95% the skills where considered capped. this meant there was always a miss chance. I also seem to recall a "crit hit level" that even without any skill you automatically hit.
This system was used for the combat and skill system. Dangerous Journeys uses a similiar system, hence why I have suggested it be explored as a basis for a game engine.
