I believe the two hits in attack are to model the Panzer attack where Tanks breakthrough the line as a shock wave, surround the enemy and cut the supply line, and make the defending enemy surrender. This way of maneuver warfare would give less casualties to the attacker, compared to the classic infantry charge and artillery barrage, which was a real meat grinder to the attacker.
But when that is said, dug in Tiger tanks defending were in fact hard targets, they were bunkers on wheels with a big gun, so maybe the two hits should be when defending too ?
My experience with house rules are that some people have difficult to accept new abilities to classic units. So maybe the only way is to introduce new units, and keep the old ones at the current system. In that case, the current Tank cost 6, A3 D3 move 2 and Blitz. Then a new heavy Tank cost 8, A4 D4 move 2 and take two hits to kill. This make sense
Next issue.
No Flash, I don’t think Tanks that just were in combat in the first territory got enough power to continue into next territory and keep on fighting. Most of them would have broke down and need to spend some time in the workshop to be fit for next battle. They could need to change tracks for sure. Refuel. Reload. etc.
In the real war, the battle would start with infantry and artillery that engaged the defenders, and make them stuck in combat. Then, when the weak spot was identified, fresh Panzer units that had been kept in reserve, would smash trough as a shock wave and take the fight to the next territory. That is how I imagine it.
Bottom line, Tanks and Mechs that were not used so far, can blitz through newly captured territory and attack the next one. Smooth and don’t violate the classic A&A engine too much.