Newt:
This is a touchy subject.
I am not sure there is any real understanding of the reason. I think it is an artificial limit meant to increase Disney's revenue. As you stated, it cannot be based on square footage. Disney has its economic reasons I suppose.
My own opinion is that based upon the square footage in a one bedroom up to 6 should be allowed. If the room occupants don't mind being crowded, and/or sleeping on the floor why should anyone else care?
That being said, 6 would result in more wear and tear and use of hot water etc. so I could see an extra daily charge, such as the $10 charged in a normal resort room for each extra adult over 2.
A few weeks back I raised the issue of whether
DVC should develop some one bedroom units with two full or queen beds in the bedroom so it could sleep 6. While some were in favor of the concept of providing a more affordable alternative for families of 5 or 6, others were against it. The thread ended up being locked. As I said, it is a touchy subject.
Absent the increased wear and tear, etc., which I agree could warrent an extra charge, it has not be rationally explained to me, why a family can't have 5 or 6 in a one bedroom unit, except, of course, the reason that it is against the rules. I guess what I mean to say is that absent Disney's interest in selling more points, I am not sure of the reason behind the rule. (other than increased wear and tear, etc., which I think could be countered with an extra charge)
Steve