Yeah, I was thinking the same thing with the O2 sensor, have everything enter the car at the same point. In order for me to do that, I wouldn't be able to reach the disconnect for the sensor. Yes, I can just unscrew it if I needed but it wasn't sitting well with me. By going over the tranny I was able to make a small coil of wire with the disconnect within reach. It was a pain in the butt to do but now I can unplug the O2 sensor and drop the downpipe in one piece if I need to.
Sounds like you're making good progress on your car.
I took a break, too cold in the garage lately.