What about the Pingel switches? Spidey has five buttons on his left: horn, hi beam, left turn, right turn, and motogadget toggle. I take it the first four (and start + run on the right housing) can't just be wired up to the existing harness?
On Spidey's bike:
Start button works as it's wired through a conventional relay.
Kill switch had to be wired through a latch relay (basically a relay that changes state in response to a momentary push button)
Turn signals were also wired through a latch relay (but aren't quite working right)
Horn was wired through a regular relay.
But latch relays are pretty finicky and I think Spidey's turn signals don't exactly work right. It's harder on his bike since I think the ECU controls the turn signals.
I was able to get my set-up working initially by using a self-canceling turn signal kit, and then wiring the push buttons normally.
Start button and horn went through a relay.
And no kill switch(!) or high-low beam control.
As for "ready to go" kits that plug directly into an existing harness... Someone is surely working on something like that (coughsworntosecrecycough)