As conventional infantry are typically spread out about any given hex they occupy, heavy Battletech-scale weapons should not be as effective against them as they are against 'hard targets' like vehicle and Mech armor. The older pre-TW rules do not account for this at all. The Total Warfare rules do . . . but (in our very humble and possibly unpopular opinion) the newer TW rules overcorrect the BMR situation and do not account for the ability to sweep streams of laser light or autocannon shells across a formation. The pendulum may have swung too far in the other direction from the BMR rules set.
As a middle ground approach, we are considering adopting the following when it comes to damaging infantry:
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1. Weapons fire against infantry deals 1d6 damage per hit, with the damage dealt 'capped' at the standard damage of the hit.
2. Machine guns, Flamers, Plasma cannons, and direct-hit artillery strikes do 2d6 damage (uncapped). Battle armor flamers/MG/APG, A-Pods, and mines do 1d6 damage (uncapped) per hit, as do artillery strikes that hit 1-hex away from the infantry.
3. When damage from such hits is to be multiplied (for infantry in the open, special anti-infantry munitions, vacuum operations, etc.) roll extra dice instead of just multiplying the result of the initial damage roll.