Well if your gonna fly the traffic pattern per the aim your also required to turn crosswind at TPA - 300....

Personally I don't think that's a good idea and would bet a 90 degree turn at 1200 feet could also get you in trouble.

I think setting TPA is silly, but I would tend to agree it's the lowest altitude your likely to get from the tower, so setting it maybe the safest course of action to prevent blowing through your assigned altitude.

Just because your cleared for a visual approach doesn't really have anything to do with traffic pattern altitude. And unless specifically cleared to enter the traffic pattern airline traffic in the terminal environment is rarely ever at the specific traffic pattern attitude. Nor are they flying standard traffic patterns. Typically they are cleared for long straight in approaches, or patterns that resemble left or right hand patterns, but more often then not the downwind/base legs are higher than could ever be considered a traffic pattern and would be more adequately described as an arrival flow.

Also I'm pretty sure airline pilots don't actually carry AFDs so knowing what the actual traffic pattern altitude is, is not possible.

Sure set 1500 and spin it higher when you get your clearance, but flying a traffic pattern as per the aim is not realistic, your not going to lose comms, squak 7600, and turn crosswind all before blowing through 1200ft in a jet, and if you do ATC will not be prepared for it.

I do totally agree this is an invention of schoolhouse guys who have to much time on their hands.