Here's a picture of the bed, just before the ATV drives up to it. Note the wheelhouses don't impinge upon the cargo bed at all.
https://specials-images.forbesimg.com/imageserve/5dd768642c8...
If you can put a 4x8 sheet of plywood in at a slope, the high end would be about 4.66 feet above the bed, if the bed is 6.5 feet long. There probably isn't enough vertical clearance for that, but it would be close. On the other hand, maybe the rear window opens and is at least four feet wide.
Such a disappointment personally, I hope they add a chassis option with an 8' bed and two seats, or maybe make the back seats removable? also they need a lumber rack. seriously, pickup trucks have lumber racks. I think they are missing out on a significant market segment of trades people by not offering it with an 8' bed(or a rack), and a foreseeable second-order effect is that it will give the Cybertruck the repute of being a poser vehicle. I like everything about it, except that it has a huge cab and a small bed.
It's a toy, this is a recreational vehicle hence the ATV. Off-roaders often need compressed air to refill tires after deflating for traction in exceptional conditions like sand and snow.
The decision to have sloped bed-rails prevents mounting toolboxes anywhere on this thing, nor can you place oversized loads across them without sliding off. That alone precludes the vast majority of work truck applications. The 1st gen Honda Ridgeline had the same defect, to a lesser degree.