[darthtrader]

Steenbarger made a good point in reference to #3. If you gave people a system that is guaranteed to make 40% a year, but it only trades 4 times a year and only holds each trade for a half hour, most people would tinker with the system and ruin it. Its not because people want to make the system more complex, its because trading is filling a "need" outside of making money and you wouldn't know what to do with your time waiting for the system to trade. While an extreme example its good to think about as far as keeping things in perspective and what the goal truely is.
As far as keeping things simple, I think this idea gets confused with keeping things simplistic. You obviously want to cut the fat and use occam's razor when judging a trading idea but that doesn't mean that keeping things simplistic is the optimal way to view a trading strategy against something as complex as the markets.