Tow/haul - Not needed on the Rivian. Tow/haul changes transmission shift points. Since the Rivian has only a single speed transmission, and more torque than just about any diesel pickup truck in first gear, there is no need for more.
Hitch cam - I think this will be standard or an option as it is available on almost all pickups now.
Exhaust braking (regen braking equivalent), etc. - I am certain regent breaking strong enough to hold speed with a trailer will be available. It would be ridiculous to waste that much energy in an EV going downhill by heating up break pads.
Electric trucks will be monster towing machines. The biggest issue is the loss of range. A 5,000 camper will cut the range in half. If you tow at max capacity, you are looking closer to 1/4th the range.
I would really love to see a hybrid electric truck with a large battery and a range extending engine.