A very good point Bally Heck, it's good to see that some other operators also consider OEI gradients for 2 engined aircraft for missed approaches.
For the aircraft that I'm responsible for, the manufacturer's Approach Climb data was thrown out (the 2.1% stuff) and data for 2.5% substituted instead to at least meet the Gross Climb requirements for missed approach.
I sneaked it in as part of the submission for the AOC (I hope that the boss isn't reading this), so we can't go back on it now.
For all of the reasons that you stated, it is very rare indeed that this 'self imposed company limit' to have any impact on landing weights, except under the most extreme of circumstances.
Old Smokey