First I would make sure the ground wires are all OK. Maybe even add a few ground wires straight from the lamps to the battery.
If that does not solve it, swap the left handlebar switchgear for another known good one from the same model/year.
put the bike on its side on some pillows, unscrew the engine, ask some mates to help lift the frame off the engine.
Frame is much easier to handle than an engine. Of course this works best when the engine is still complete but it should be possible.
sounds like ignition problem to me. Check all the electrical connections are clean and tight. Might be some resonation-induced vibrations at 7000 rpm causing trouble.
to be honest, after 20 years of being a bike mechanic, in 90% of the cases I reuse the seals if they are not damaged. A good clean is usually enough. Make sure you thoroughly clean the grooves where the seals sit.
Welcome on OSS. I've been in Reno in the '90s, the thing I liked most was the proximity of Yosemite National Park.
Anyway nice bike. I don't know about the Busa front end.