The VIN is only needed when the X-Plan purchase is being completed. Once you have a PIN you are not even limited as to what you buy. You could walk in to buy a Maverick and leave with a Mustang GT Convertible!
Thanks for asking this question...I came here to try to sort that decision for myself! I *have* a Ranger XLT FX4 for flat towing behind the motorhome and rock crawling. It also tows what I need to tow. The Maverick will replace my Fusion which I use for part running, groceries, hauling ladders...