In the Battletech Universe, unless you're facing a Clan unit, isn't a straight up "mech vs. mech" battle something commanders instinctively try to avoid? If that is the case, doesn't it make lots of sense to go heavy with lots of light, long range autocannons as you can use them effectively against vehicles, aerospace fighters, elementals, protomechs, infantry, and pretty much everything aside from 'mechs of comparable tonnage.?