I like it the way it is. Why discourage solo bombing missions? I know it may not be historically accurate, but neither is field capture the way it is...but since this is a flight sim, I think the current field capture scheme and bombing accuracy fits.
Now, I don't have the huge problem with stratobuffs that some people do, but limiting the zoom capability for bombers, based on their service ceiling might be a decent idea. I can currently go up to 20k in any bomber, and take out any target at any field with 100% accuracy, if not damn near that. When I was a stupid newbie (instead of a stupid oldie), I didnt' RTFM and consequently had no idea there was a zoom. As a direct result my hangar bombing was at about 60% and there was no way I could see, much less take out ack. If ya limited the zoom, it could make bombing a little harder, but still have 100% accuracy at reasonable altitudes, and add some real difficulty as you soared into the stratosphere

In any case, realistic or no, I think the way the bombers work now is just fine. If you spend the time to take up a bomber, risk meeting NMEs on the way, you deserve to be able to drop your eggs on target. But, I can see the argument to punish the guys who like to soar high in the stratosphere tho'.
SOB