I think you have a lot more investigating to do before you can say with certainty that it's the bottom bracket. Skewers, hubs, pedals, cleats, loose cabling even. Hell I had a squeak that I could not figure out where it was, it happened every time at the same position of the pedal stroke under load. Turned out to be the headset bearings being completely trashed. Made no goddamn sense, but when they were replaced, squeak went away.