I feel much the same way as you do, but I figure they should have been able to stretch out the body in the rear of the plane near the galley. They could have tied it down and covered it with something so people using the head wouldn’t have to view it directly. And the flight attendants might have had to extend their legs over the body, but...if the flight is full, what are you going to do?
I don’t like that they put the body in a seat next to someone. There must have been a better solution, but...I wasn’t there, so I can’t say for sure.
If the plane had had at least one lavatory they could spare, they should have locked the corpse into it.
Regards,