Assuming Gene had the resources and will, how much would you pay for a kit that would allow you to convert a PM or Airborne (or even a FF with some extra cabinet work) to a Kingpin? Assume the kit comes with -
1. Translite;
2. Cabinet Art;
3. ROM chips;
4. Fully populated and wired playfield (ie direct swap and drop in ready to go).
This would take the whole project away from worries about the problem chip, and indeed any board set issues at all.
Perhaps factor in the cost of the base game when you decide your figure.