I drive an Astrovan. The roof is much higher than the Model X.
I used to put my kayaks and my bikes on the roof, but after knocking the bikes into trees, houses, and other low hanging objects, I started using a hitch mounted bike rack.
It is much easier to load the bikes, but really interferes with acces to the rear of the vehicle for loading and unloading things, even when it is tilted back away from the doors.
I only mount the rack when I need to haul bikes. It's just too much in the way for everyday use, so when I want to haul bikes, I have to go through the extra steps of attatching the rack first.
I still load the kayaks on the roof, so when I haul both bikes and kayaks, I have ample room for both. I use the kayaks very frequently, and sometimes leave them on the roof for several days.
Lower gas mileage is not enough of a concern to make me want to not have roof racks, since I use them all the time.
I also use the racks to load canoes, lumber, furniture, and anything light enough to lift over my head.
I use my vehicles to haul many things. I would want to use the Model X to do this as well.
I don't want to haul a trailer around and have another item to maintain, and have to find a place to store it.
On the rare occasion that I need to haul heavy items like a load of firewood, U-Haul is a mile away, I just rent a trailer for the day.
If I buy a Model X, it will have to have a Roof Rack permanently mounted, and sturdy enough to cary a several large kayaks long distances at highway speeds.