In the military, concealment is not an issue. Weight is more of an issue and that is better solved with holster and suspension designed into the uniform IMHO. This would have kept the 1911 around longer.
They dealt with the weight of the weapon rather than the perceived weight as handled by modern suspension and holster systems which can be engineered without the conceal carry issues needed in the civilian world.
I'm not sure training is really that big an issue, either. I recall my first Chief saying, "Mr. Drill, you give a sailor a cast-iron cannonball and in 24 hours he'll either lose it or [mess] it up!" but in practice it really wasn't all that bad. Lose a single cartridge over the side, though, and the consensus was that you might be better off jumping in after it.