Serious question, how is that different from Contests? That already takes into consideration base skill, situational circumstance modifiers, random effects, and margins of success.
I'm not trying to be critical or flippant, it just sincerely sounds to me like everything you've described (skill contests, combat skills, uniting disparate genres under one system) is describing GURPS. I'm genuinely curious what the difference is, I must be missing something.