This change would only really effect larger waves, and attacking high-turret targets.
And those larger waves are what you will be seeing more of. High LB fleets will be stronger for it and that is something I believe is unwarranted.
For example, you have 10 bombers and 6 fighters (just to have an even 16 LB) going up against an oberon. For the sake of the example, assume they don't suffer casualties before turret fire. Under the current rules, each surviving bomber rolls (d6-5) and since fighters die first, all 10 bombers roll which nets you something like two attacks. Since you have at least 5 fighters with them you add another 5 attacks to that so a total of around 7 attacks against the 5+ armor.
Under your proposal, we would still have around 4 fighters remaining which lets ALL of the bomber roll (d6-1). Now I'm not going to take the time to figure out what they would roll on average for their runs, but you've completely reversed the odds. Where the bombers originally had 16% odds of getting at least one attack run, they now have 84% odds of getting at least one run since they only need a 2+ on the d6 roll to get an attack.
In our example, that equals out of eight of the bombers getting at least one attack run which is the low end. All it takes is a couple of those rolling 4+ to significantly increase the number of attacks. Say, for the sake of example, you roll 1,1,2,2,2,2,4,4,4,4. With your rules, we get 16 attack runs while with the current system we would only get five. To me, that's far too much of a boost.
Perhaps instead of all this contrivance, just say that
any surviving fighters allow bombers to reroll their dice if they failed to score higher than the targets turret value.basically it grants the bombers another shot at an attack run without the fighters themselves granting bonus attacks. It doesn't guarantee any extra attacks, but it could net you a few.