From taking a look at the wiring diagram it looks like it would be simple enough to connect the gray/blue and gray/red wires that go to the kill switch together and then connect the key switch wires, white/black and brown/blue to the control switch. all the current load pretty much goes through relays and either switch kills fuel pump ignition etc.
I have removed the key cylinder from my cup bike. The base is a rotary switch that can be removed which I placed in the on position then covered with a plastic bag and electrical tape. Now the kill switch turns the bike on or off.