This thread has been very insightful for me as I have fallen victim to a lot of foolishness the past 18 months. By no means am I saying you are foolish Coop, but I totally understand your desire to overthink everything and find ways to work harder or reinvent the wheel. I never saw a lift I wouldn't try to work into my routine, always thinking I would hit every conceivable muscle in my body from every conceivable angle and somehow I would create a perfectly balanced body, whatever that means.
Finally, it struck me that I will never be using a single arm incline cable pull or a concentric DB preacher curl in real life. If I want to pick something up in my garage or throw my children up when we play, I'm not really going to be any better at it because I did decline flys the day before. At least your modifications have some basis in reality because of your impingment and uber-enthusiasm, mine was just idiocy apparently.
It was an epiphany. Only took 18 months to hit me. I think you are ahead of the game.