Much of Warmoth's finish process is done in batch runs too.
The likeliness of getting enough orders to justify a specific run of finishes on enough bodies and/or necks would have to be significant to justify labor costs of setup for that special run, which would also bring "opportunity cost" into the discussion due to the fact that while this run is happening, the normal production run is set aside, delaying it further.
Simply put, it's likely not profitable as Warmoth can foresee it. All they have to do is run a report on how many requests have come in, either by phone or by email, and do a projection of what this would cost to do, and see if they can foresee any profitability in it.
If they don't smell money attached to the idea, then the idea is likely unprofitable, and therefore, not viable.
They are a business, and a business exists to turn a profit.
Once you remove the emotion from it, that's what it is.