Sure, but there comes a point of diminishing returns. Steel frames and solid axles are used because it's easy to get the necessary load bearing capacity from them. The F150 is the most popular selling pickup truck and it does not have 15K towing capability. Over engineering a Tesla Pickup Truck to reach a tiny niche of use capability does not seem like a rational use of design, and would probably not result in an affordable vehicle for the general F150 buying crowd.
Hold it! Tesla is coming out with a F150 style pick-up truck? When can I make a reservation? Do I have to cancel my Model-X reservation or can I transfer it to the pick-up? Is it expected to be available in 6 months (I think I can wait that long)? Wait, I already did this 3.5 years ago with the Model-S. I'm not going to make that mistake again...