I am 90% positive that the force field bearers were not being damaged by outgoing fire, at least in the most recent versions that I was looking at. I know that at one point in the past they were damaging themselves and other ships were damaging them, but that was fixed at some point before the present. I think that was fixed before 2.0, but I am not 100% certain.
To be honest, eRe4s3r, I've never particularly liked that mechanic either -- I have always viewed it as a necessary evil, and have been hoping a better solution would occur to someone. And lo! Here comes yours.
I think that reducing power to 25% instead of 50% is a more effective number, but we'll see how that plays in practice. This would be only for the blue player force fields, not the yellow forcefields of the AI, which I don't want to mess with the balance of. Having force fields used as a "force multiplier" is something I have always liked for the AI, it makes for interesting gameplay, but it's not a good thing for human players as it is far too easy to abuse. The AI is rulebound so that it never abuses it, but the human players are not.
I'm also making the other smaller force fields (like the force field bearers) now be yellow instead of blue, to show that they are also the kind that does not cause damage penalties. Only the blue will, and no forcefields will be damaged by outgoing fire.