Cutman, I think your idea is good. My only concern is that anytime you make a cut that big, you take a chance that it may not heal over well. It likely will heal over eventually, but there is a chance of getting a cavity started before it completely heals. But, if it were mine, I would probably do what you are suggesting. I did that to one of my mom's apple trees a few years ago, and it worked out fine; however, that tree was not quite as large as your tree.
I will also mention that if you have a backhoe, you could dig up the tree (with a massive root ball) and straighten it. We successfully moved some fruit trees that big a few years ago, and all of them lived. If you did that, I would suggest some heavy bracing for a few years until the roots reestablish well, or you might end up with the problem repeated. You would also need to do it in the fall after it goes dormant.