I have found that the units that benefit the most in the transfer over to Alpha Strike are the ones which have a large number of smaller weapons as opposed to those with a small number of heavy hitting weapons.
Personally, I think there should be a special called "Headcapper" or HC on the sheet. Any mech with a weapon capable of doing 12 or more damage in Classic would have the HEADCAPPER special ability.
Whenever a Mech with this special ability hits a target of the type BM, they roll on the critical table ignoring all results other than a 12.
This roll is not affected by the CR special ability.
If using multiple dice rolls, you must designate one specific pair of dice to the HC special ability, if that die rolls a hit, then the attacking player rolls on the critical table ignoring all results other than a 12, this roll is not affected by the CR special ability.