Oof, thanks for the correction. Tangling with the ECU is way outside of my comfort range, and I'm glad you stepped in to squash the "I heard that you could..."
Yeah. I considered telling people to just do that, but when you consider these wires are outside and could possibly fall off, drag on the ground, arc on the frame, etc. I reconsidered. My relay setup still uses the ground from the factory plug, but only as a trigger for the relays. So in the event of a short, no power can be sent inadvertently through the factory wiring.