There will be no aftermarket "pluggable batteries for extra range" if the hardware on the truck doesn't support them.I haven't seen the truck bed mounted battery pack mentioned in a while:
"Rivian says that its battery pack may be available in several configurations to provide varying amounts of power and weigh "several hundred pounds or more," meaning that the company could theoretically sell 10-kilowatt-hour or 20-kWh packs depending on a customer's needs."
Even if Rivian doesn't do this - I have to believe an aftermarket solution will emerge. And I bet it would cost less than $17k
Which it currently does not.
They have a patent on the concept but have absolutely not implemented it on the current R1T.