design questions can be challenging

So my lack of activity on this here webzone should not be taken to mean I haven't worked on my game design project. Not working particularly hard on it, but I have been working. I can't prioritize it above family or my job, but I can (reluctantly) give it time in preference to playing other games. And I should if I really want to complete it. I have been noodling over some questions. I made some early arbitrary decisions "I would rather throw a handful of d6s than use d% or something else" and "Levels should be determined by total number of skill points, and be used for hitpoints and untrained skills", but other decisions have not been easy. What should be the basic scale for skills? what is weak, and what is strong? How many skills should there be? should attack/defense be separated, or one aggregate skill with conditional modifiers? I know to "keep it simple, stupid" but the simulationist in me wants granularity.