It's defenitely a good idea, but I don't think the wideband O2 sennsor would last long enough under constant, regular driving conditions. (which it what it would see, as all of us here don't have dedicated race cars) They aren't designed as ruggedly as regular automotive O2 sensors. And, they are far more expensive, so you'd be spending alot of money replacing wideband O2 sensors over time.

If you are planning on using the megasquirt, I wouldn't worry so much about the fact that it is not sequential. I know sequential is better, but cars have been running on batch injection, throttle body injection, and carbuerators for a long time, so I think you'll be ok :)