From the OP's post he sounded like an intelligent man who wrote a cogent and well though out post. I wrote my answer geared towards him, not to you or anyone else here.
I saw no need to go into minute detail, as the OP has a grasp on the situation. I stated it was doable, and advised him to practice. At that point it's all up to the OP to:
1. Practice shooting with his middle finger
2. Decide whether or not it works for HIM
This is one of those posts that NO ONE can give the 100% sure-fire answer to. The only way to solve the issue is for the OP himself to go to the range and practice the new technique. If it doesn't work for him, then it doesn't work for him, but only he can answer that question. You and I can argue until the cows come home, but nothing we say will solve the OP's issue.
Over the more than 2 decades I've been doing firearms instruction I've have plenty of students that have had issues of one sort or the other, whether due to injuries, age, or a problem they've had since birth. I've learned that there are no cookie cutter or one-size-fits-all answers. Start with the easiest solution and work your way down the list from there. Using the middle finger is, in my book, the easiest solution.
If the middle finger doesn't work for the OP, then I would go to other options, like:
1. Switching hands, if the OP doesn't have the same issues with his other index finger. This has worked for some people.
2. Going to a different gun that doesn't have that long, heavy DA pull (which has been somewhat covered previously in this post). The OP already stated that a 1911 is a no-go, so I would have suggested something striker-fired, like a Glock/S&W M&P/SAI XD/HK VP9/Steyr M-series/etc.
I've already stated that it was apparent that we wouldn't see eye to eye on this. You're wasting your time trying to continue pounding your points home.