I created my own unique system years ago, right from the beginning. A little talent, a little devotion and you can build a better mousetrap. I believe it was Arnold Snyder that said something along the lines of "A truly successful player is not one that is the best at following what the "authorities" say to do. They are instead capable of innovations and have the ability to think for themselves".
I know someone who created a system for a side-bet (card values, and betting ramp). Does that count?
If you use a broader definition, where "system" incorporates the set of specific index plays used as well as betting plans that incorporate various levels of camouflage, then I have created several "systems" that I use depending on the level of heat, etc at a particular shop.