Searched but didn't find a suggestion for a removable trunk lid. This would allow large objects in "Hauling" mode. Bicycle(s), electric lawnmower are some items I'd use it for. Add Weathertech rubber matt, D rings for ratchet straps that secure a load & something like a durable rubber 'pool noodle' to protect car body edge.
Other reasons for removable trunk lid? Tailgating, camping, emergency response. Remove gear from car & use it as bed. Attach tent to opening. If lid has PV, aim at best angle for sunshine & run cable to car for best charging.
I'd be OK if speed had to be limited to prevent highway use, ie 45MPH. I don't see why but for liability. The car would know when lid is removed. Just an idea.
This is going to produce tons of drag.
One could likely DIY. The hatch almost certainly IS removable, with difficulty (not impossible), & a yacht canvas shop could make you the tent.
This was asked.....Aptera said that they are not making it removable “at this time”.