Add Variety not needless Complexity
You can usually get interesting result by hijacking existing material and concepts. You don't need to totally reinvent the wheel, often you can just grind the serial numbers off something else, put new paint on it, and drop it into the game as a new rule. But don't make new rules just because you think another 7 moving parts is going to make it 'good'; sure lots of people love their crunch, but if you can get the same variety without making it a Rube-Goldberg of die rolls and tables and whatever else... then you've achieved your objective.