If the guy is being a PITA, let him build it then have zoning show up and make him remove it. Nothing hurts more like hitting him where it counts.
I'd be hesitant to go this route. All the building official has to ask is how you became aware of the problem and when the answer is "we knew before he started but we didn't stop him until now", that isn't going to go well.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
