Teslas are fine(ish) cars, but they seem resistant to forming deals to provide skateboards to niche applications, like Chinese companies are doing. There’s big money there!
While more complex unibody construction is generally better than frame on chassis. There is a reason most cars and SUVs are unibody and those won't change. Thus skateboard isn't a useful idea.
Trucks often are frame on chassis though, so if all you are going after is the truck market then skateboard makes sense. A worthwhile market for sure, but not as big as you think it is
In case the jargon isn't transparent, in automotive a 'skateboard' is roughly a flat frame with batteries, motor, motor controller, and suspension onto which you can bolt the rest. A vehicle platform, really.
OP is referring to the battery, power electronics and drivetrain. If you picture lifting the body off - sorta looks like a skateboard.
(although cars like Tesla are highly integrated - there's probably still good money to be made in selling the "dev kit")