Overall I'm good with the change. Looking back at my 'Mechs that I still have to fix though arguably are being done on the old rules, here's what I've got.
Marauder crits - Left Arm Actuator (destroyed, no change), Engine - 3 hits (multi-crit, repairable, not impacted, no change)
Banshee crits - Right Hip (destroyed, no change), HGR Ammo bin (destroyed, no change), LA PPC (1 crit of 3, would require a 2d6 roll)
Battlemaster crits - Engine - 1 hit (multi-crit, repairable, not impacted, no change), DHS (1 crit of 3, would require a 2d6 roll)
Shadow Cat D (salvage) crits - 2 gyro (multi-crit, repairable, not impacted, no change), RT destroyed, everything already lost, no change
Net effect: Two extra rolls during repairs, of which there are already going to be a ton, so not a significant add. I'm likely to lose 1 PPC and 1 DHS in a battle where 3 of my units took at least 2 crits worth of internal damage. Not a huge deal.
I may need to manage my warehouse a bit differently. It increases the likelihood that I'm out of key parts for specific mechs, so I may rethink lance config.
Autocannons are the big losers as they are high number of crits to weight. Omnis just got even more useful. Whether you have your ideal mix of weapons per mission may be different, but you're likely still able to field all of your preferred units regardless of this change. Net, still happy to see what happens with this.