I’m pretty sure there would be a market too, but unfortunately I think these days they would still cost a fortune. They would only lack the facings of the Customs and I’m not sure the electronics would really be any/much cheaper to manufacture than the Custom ones; after all, the pickups are the same. Even passive, you’d just be losing the cost of the filters.
Of course it may be that if you asked nicely and paid sufficient funds, Paul may make you one anyway. Albeit they can’t reproduce the moulded scratchplate, certainly for one-offs, as this is something I discussed when I first got my Pro and was thinking of making it passive a la Leigh Gorman. Of course if they ever brought back the Pros, they could probably get the scratch plates done en masse, but again, would it be cost effective?