Devleigh:
Not designed for remote starting/stopping only has a key switch. ..... Gotta love a challenge
Interesting idea. I have a "dumb" generator at the house that might be in need of an upgrade.
So were you looking at bypassing the starter switch with a relay between common & positive or go series with a new wire that runs through the relay and into the starter?
How will the Arduino know to open/close the relay(s)? Wireless? Wired sensor on mains either ran to the generator or the transfer switch?
Also consider a solution that monitors the generator circuit breaker in case it trips. The generator will still run but not produce any power which could trigger the Arduino to "start" the generator.