Main switch is hand operated switch, that should take it easily. Used in case of fire, for example, to connect all the electric power off.
Reason for using aux 4 is, that in FIM-E rules there is :
"All gasoline or methanol burning motorcycles must be equipped with an electrical contact which disconnects all electricity to the engine (and nitrous oxide system, if used) and including electric fuel pumps if the rider should lose control of the motorcycle." (=wrist strap)
So there is wrist strap, run/stop-button and emergency-button that are doing basically same thing, but with little differently. Off course this could be done with relays, but I thought this would simplify wiring and do it with the ECU.
Emergency button is something we just do to every bike in our team. I am lying very low on my bike. If I lose the control of the bike and will not be able to let go of the gas or lift it, there if a button in top of your front fork, that you can try to hit with your forehead and it will kill the bike for the moment. Sounds little bit funny, but that is just something that we have agreed to do. We have to remember, that we are trying to build +500 hp bike with no wheelie bars that will weight less than 250 kg. Team is not very experienced at this level and bike (including slider clutch) is all new, so there are lots of things that can go wrong amazingly fast. If am not very over worried of anything usually, but now I have to admit, that now I have certain respect for the bike and I am thinking little bit of safety also.. :-)
There are several sensor ground wires and +5v wires in Link wiring loom Most of them are used for critical sensors, but there is one or two left and I still have lots of sensors that I need to get powered (Rear swing height, gear position sensor, puel pressure.. Etc.)
So, is there any limit for sensors and is there rule, that some types of sensors should not connect to same +5v power or sensor ground. Mostly Hall, pressure, and travel sensors.
Edit: Hall doesn't need sensor ground, but +8v, shared with cam sensor. And sensor ground is already divided in the loom, so it should be OK to divide again later in loom.