Force fields should still be quite viable, especially in concert with gravity turrets being placed a bit away to slow the starships down. It may be that starship's bonuses are out of whack with the current methods of force fields working, which I would need to address separately. I think a rebalance there could be very good. But there were just too many exploits possible with the old way the force fields worked. The goal of the new method is to make them still be useful for actually protecting structures, but not as a force multiplier for force fields.
Regarding the Mad Bomber AI Type, about the only thing it has going for it is its offensive capabilities, as it is pretty skeletal on defense. The bomber starships may need to be adjusted somewhat against turrets, but this is a separate issue. The old method of handling force fields basically allowed them to work as an incredible force multiplier, so players could do things like putting them over a wormhole with 200+ high level turrets under them, and they would chew through 10,000+ units. This sort of exploit is simply game-breaking, and the only way to solve it is to not have turrets be effective under force fields (unless I were to increase the footprint size of turrets significantly, but that seems a little strange).
Unrelated to this... I haven't been around much the last few days, but I've had a bit of personal tragedy over the weekend that I've been dealing with. Basically, my wife was pregnant with our first child (which we were super excited about), but she miscarried. It's something that happens a lot, unfortunately, but still quite difficult. I was on the fence about whether to mention this on the forums at all or not, but I figure it is better to be open about what's going on rather than just mysteriously dropping off for days and then coming back a bit more moody.
Anyway, I should be mostly back in the saddle tomorrow, and will be moving toward the next official release this week.