Battletech does limit this, in that while a fighter certainly is allowed to drop all of its bombs in a single dive-bombing attack, doing so is incredibly risky.
Carrying that many bombs slows down the fighter immensely and makes it easy prey to your own fighters(this is why you should always have air cover of your own if there is any chance at all you'll be facing enemy air assets). If your opponent wants the dive bomber to get through he must provide escorts, and the cost of those escorts will subtract from the points(or however you balance your games) he has available for ground forces, leaving you with the advantage down there even after he makes his bombing run.
In addition, the two altitude levels dive bombers are required to shed during the attack makes them incredibly vulnerable to anti-air fire during that turn. You may not always be able to prevent a dive-bombing attack, but if it's against units with that much firepower you can pretty much guarantee that there won't be a second attack, because the fighter will be dead.
Also, I'll be moving this to the Total Warfare forum shortly.