Back to the "Build to order" idea...
Every car, truck, SUV, and CUV manufacturer has been doing this for decades...
Dealerships always have units in stock, because they need to have a product that you can put your hands (and eyes!) on.
They'll try to sell you the on the lot unit; because that's the one they're already paying for.
You CAN order your RV (We did!): it just takes time for it to be built.
But you still are limited to the options that are listed in the playbook. They could (but won't) built you a 17 foot-long diesel pusher with 605 horsepower, and bunk beds....
They need to have the "buy & build in bulk" discounts available...
Unless you're willing to open up your wallet, and REALLY get serious about paying for it.