Rather than chair slots I’d rather see a collapsing wagon to haul all the kids crap you were mentioning. Could use for sports (been there-done that), or groceries or beach “stuff”, etc…. Even if it was a slot under the vehicle -sorta like a U-haul truck had the slide and hide rampI don't know if this would be better as an accessory or a built in, but let's use the electric battery to our benefit!
Besides having an inverter for AC power (possibly even with 240V?)
Have 1-2 built in, compressor driven coolers, ideally some that can be left on when the car is off as long as the projected state of charge will be high enough. You could have the software calculate that for the driver so that if someone say leaves their house with a 300 mile range, drives 50 miles out to camp, it could run but ensure it warns you and shuts the coolers off before it runs the traction battery down too low to get home. This could be nice for those that always like to keep cold beverages in the car for themselves/kids, but are plugging the truck in at night at home too. The cooler could stay on "continuously" if desired and it would just slightly decrease the range.
Having a way to tap into the power in an elegant way for camp lights, either on the roof or underneath that would be very dimmable so they could create a soft glow when desired.
I also love the other users' suggestions about having a couple of "always charged" flashlights (maybe one in the front and one in the cargo area) so that I never have to worry that I have them ready.
While not everyone would want it, you could make an optional "tailgate package" that could incorporate a TV on the inside of the tailgate to catch the pregame as you tailgate waiting for the game you're there for. Bonus points if it has an HDTV antenna unobtrusively incorporated or along the roof rack so that you can pick up the local channels.
I think this would be an option, as a lot of folks wouldn't care, but some people would love it and it would absolutely set the truck apart for tailgating, camping, going to the beach, etc.
Would also love if there are camp chairs that can really compactly slide into slots in the body/cargo area so you could "always" have them with you having something clogging up the trunk area. My kids play sports and we're forever dragging a couple of camp chairs out of the trunk or loading them in (along with beverages - see above) to go to games/practice, etc. It would be a killer feature to have first aid kit, camp chairs, and a cooler onboard at all times.
Might not be for everyone but I like your thinking. Also would open up a branding collaboration