Don't be so negative.
Since I see no reason for the allowing simultaneous transmit in a colission avoidance setup, I stated my experience with collision detection vs collision avoidance, I did not comment on your suggestion.
My attitude towards colission detection instead of colission avoidance is definitely negative.
The "no extra load if simultaneous transmit" you suggest, you can take or leave, especially today where the modern 485 transcievers gladly accept simulatanous transmit without popping.


Erik