car alarm with keyless start

I have a 1995 saturn SL with a Hornet 740T alarm installed. my alarm has an Aux output that is designed to power relays, etc. I was thinking of using this to make a keyless (not remote) start. what i was thinking was to use an SCR to close the three circuits that the key cylinder normally closes when you put it in the "run" position. i would then have a normally-closed pushbutton to open the circuit, thereby turning the car off. one of the circuits the key closes in the "run" position is the ACC circuit. i was thinking i'd have that of course powered by the same SCR, and that i would also have a switch in parallel so i could run the radio, etc, without the car on. i need to close three circuits with one SCR, so clearly some relays are needed. i was wondering if it would be best to have the SCR only power these three relays, or if i could have the SCR power one of these circuits, and add two relays in-line. it feels like i'm missing a detail here, but i can't think of anything. the big question here is does anyone see anything wrong here or any details i've overlooked?

i had the best idea at one point in my life, i found a sent of push buttons from a rollercoaster panel, RED / YELLOW /GREEN, i think those would have been a sweet idea to hook up as a push to start setup in a center console....try maybe looking for something like that...red-shutdown, yellow-ignotion on, green - engine start.