I would normally agree with you. The problem is size. I don't have room for two relays. I know it exists because a device was made that does what i am looking to do. Problem is that person is no longer around nor is his company.
Also another issue is i can not put this relay pre-starter relay. Due to insurance laws this cuircuit needs to be mounted to the starter itself with a tamper resistant caseing so that a car thief can not simply bridge/ bypass the relay and start it. (These vehicles do not have a ecu.