The worst that could happen by splicing into the yellow wire, is either one of the main ignition fuses will pop, or the dash will catch fire, no big deal...
I cut the orange wire and put a relay between them. amazingly no fires or popped fuses!!
are you saying that as a precaution so that people who have no prior experience don't go hacking into their wiring? Because putting a relay between 2 cut wires is not going to start a fire.....