Sheep Guts, I take it from your profile that your perspective is as a passenger? Nothing wrong with that, but you are missing a couple of points in your suggestions.
Modern large jet aircraft don't just load the catering on the starboard side; all the freight and baggage is loaded that side too. The complexities of trying to arrange boarding access via both sides of the aircraft are immense, and unlikely to be practical. It is possible, however (if unlikely), that 3 (2 main deck, one upper) jetways could be used on the port side - if airports are prepared to invest the money! Most airports rely on one jetway - even for a B747 - but there are more and more utilising 2, which makes a significant difference to boarding/disembarkation times.
The 'slow' A340 you refer to cruises at M0.82 (A343) or M0.83 (A346). Not as fast as the B744's M0.855, but the difference is not that significant to the passenger. And yes, I know that the 744 can cruise faster than that, just as the 340 can cruise faster than its normal speeds, but the difference remains relatively small.