If you are worried about the back-fed cranking power to the ECU, you can put a diode across the ballast resistor. Since this back feeds the ECU, Voltage Regulator, Alternator Field, and what ever else is connected to the Ignition 1 circuit, the diode should be able to handle several Amps.
Thinking something like the 15SQ045?
https://www.smc-diodes.com/propdf/15SQ045%20N1007%20REV.C.pdf