If you feed the control side of your button from ign1 it will only engage the starter when the key is on. If you go 12v battery it will crank at any time, only start when the key is on. Either way the starter will not crank when engine is running because the PCM sees rpm and protects against double start.
Just saw this topic on another thread, and I would try jumping ign1 and ign2 first, it's easy and if it doesn't work you can add the button. Mine has started every time this way in 1200+ miles... So far, I'm sure I just jinxed myself...