Another one:
Infantry Ranges (that is, ranges of weapons relative to unit types they're pointed at.)
The common justification for the short-short-short range of battletech weapons, is Battlmech armors. ATOW gives significantly longer ranges for rifles and machineguns and the like vs. human beings, than the base ranges in TM or standard Battletech.
Armor and Sensor jamming, among some other potentials.
I apologize, but I want to take a moment to play temporary devil's advocate for moment about a concept.
People complain about the Napoleonic formations and the fact that Conventional Infantry get the same benefits of armored targets when it comes to ranges. I happen to be one of them.
But, I recall that some of the writers have professed to adhering to the idea of ambient ECM and sensor jamming being a large factor behind the ranges. It's possible to envision that the Conventional Infantry have to deploy in platoons so that their miniscule sensor jamming packages which comes with their standard gear is more powerful and effective when they're in large numbers, close together. This allows them to march up in clear line of sight and not have to worry about getting sniped at Line of Sight ranges by something which relies heavily on sensors to fire a laser with pinpoint accuracy.
This has never been officially declared as the case. But, if they were to do so, I might be able to work with it.
However, it does create it's own conceptual problems. For instance, what happens when you start to weaken the field when troopers start dropping? Also, if they're able to network sensor jamming across multiple bodies, how come they can't do the same with sensor packages to help get the ranges for their heavy anti-armor weapons to reach the same ranges as what's found on Combat Vehicles like tanks, mechs and power armor?
And, it fails when you realize that it doesn't effect the Mark 1 eyeball or general cameras.
(And, what is the mk 1 eyeball but a gelatinous camera?) The only way to jam that is to a) overpower it with light and blind it, or b) change how it perceives the data, which can include camouflage or actively hacking and rewriting the interpretive subroutines.
[/Devil's Advocate]