I did a custom run with Racing Champions in the past, and the minimum (after extended negotiations!) was 15,000 pieces. I suspect that HW woud be much higher. However, it appears that the original has sold well enough to justify doing a second run with the white wheels and white cladding; so it could be assumed that they could make a go of it with a third run if it didn't involve a total re-tooling. The cladding is plastic (and hence cheaper to re-tool), so maybe they could make the wheel opennings larger and put larger wheels on it, as well as make it a different color & put in the tinted windows that were used on the silver version. Black (I may be biased!) with tinted windows and larger wheels would look good - or maybe an orange Geolander.
What it will probably take is an advocate to push this, as there is no way to approach it from the "guaranteed order" aspect. If your guy could look at the sales numbers and justify another version internally based on that - we may have a shot. Maybe touting the collector status of the vehicle and the replicas could help as well. I think one of their larger (think they are called Muscle Machines??) versions tricked out would be VERY cool, and very sellable!
"If you're not living on the edge --- you're taking up too much space!!"