What we 740 and 740b portrait-mode users need is for the entire system to boot up in portrait mode. We never use landscape mode when the 740 is mounted in the airplane.
Furthermore, it looks really flaky while booting up. Several passengers have commented unkindly about this display:
And imagine trying to make a 740 connect to a new wifi router or download data when it's in portrait orientation. You either have to tilt your head sideways, or take the device out of the panel or dock and rotate it manually.