Bombers add counterattack but they don’t sit on the seazone and so they don’t defend you (except in the sense that they threaten whatever japan has left once its your turn).
In 42.2 (and 42.3) unless you kill Japan’s Java Fleet or it makes some serious money mistakes, it can build against you 1:1. This means that if you buy subs or bombers (or other junk like transports that do nothing to protect your fleet in place) japan will have more hits on both offense and defense (its usually about 14 Japan Naval hits to 16-17 USA and allied hits if the allies play super-optimally) when we are talking about a face to face confrontation in a classic naval battle.
The USA is just really hampered here; in 42.3 they need to spend 100% atlantic to even try the KGF. In 42.2, they can buy optimally (bbs, dd, carriers and every fighter) and still only match, not beat Japan.
Many times whether the USA steps up on defense or it uses the bombers etc to attack, they lose it all during that fairly even battle and then Japan can do whatever it likes. this makes KJF even more suspect, in these editions.
If you and/or your friend are really upset about the loss of the original MB A&A tech chart, pretty sure that method and chart are still 100% compatible with the current 1942.2 game if you really wanted it (I’m not talking about game-balance, but mechanically speaking, it would still work).
The old method was spend 5 IPCs per die you wanted to roll… if you spent 20 IPCs, that’s four die rolls. You’d roll the dice… each result of “6” was a breakthrough and you’d then reroll for each breakthrough and apply it to this chart:
Jet Power (fighters defend at 5)
Rockets (1 rocket attack on enemy industry a turn for any AAA within 3 spaces of an enemy Plant… 1D6 IPC loss to enemy)
Super Subs (subs attack at 3)
Long Range aircraft (all aircraft have 2 more range)
Industrial Technology (all units are 1 IPC less)
Heavy Bombers (all bombers roll 3 dice instead of 1… note this essentially ended the game… lol).
If it’s really a big deal to you guys, all the above rules would work mechanically with A&A 1942.2… however, not all are balanced, especially Heavy Bombers, but that could be changed (maybe roll 3 dice and choose your favorite of the three).
There’s lots of custom rules for tech research… its not hard to either add the original rules, use someone elses posted on the forum, or just make up your own house rules. In any case, this is one of the easiest rules to add back into the game if you really miss it.