Let me throw a wrench into the mix, now, while obviously I couldn't make armor out of REAL bone (Well, ok, I could, but it might be quite expensive and somewhat unethical

What is the important part? Authenticity? Weight? The above mentioned attempt at not looking like pop-cans glued together?
I know I have a hard time selling the game to LARP newbies who like to play the buff warrior types when I have to tell them "Well, you do have to have REAL armor, or it doesn't count for points. Yeah, I know it costs at least $300 for a set of armor that will count as heavy, but them's the breaks."
In my opinion, if metal makes up a large percentage of the armor (Chainmail with rings smaller than a certain size should count, while thin-plated leather that only covers a small area of the front and back might not, for example), it should be able to count as heavy. Metal is expensive and home-made metal armor takes considerable time to make. And chainmail is both heavy and can be quite uncomfortable, regardless of it's composition.
I understand we don't want people walking in with silly costumes, however, I do want to pick a bone with the people who are REALLY looking for realism in a fantasy LARP. We already have to accept that people can be raised from the dead, spells can be thrown around and you can make a sword in an hour. I don't necessarily think realism should be the number one concern, but I do understand that balance should be.
I actually like the idea of giving people who wear heavier armor more combat reflexes as an exchange for wearing something that hampers their movement. I guess I must not have played when soak was really high, but I think we only have a few builds/characters with uber-soak rather than the majority, and it's these builds that need to be looked at. When you have a majority of characters that can be knocked down in four hits or less (Usually much less, since most things swing more than one for some reason, I think that REALLY needs to be looked at too...last game EVERY single wandering monster I ran into swung for at least quick 2's, there were several that swung 2 and poison, but none that swung less than 2), there is something of a problem. (I think that's too deadly

Really, I don't have a problem with the GMs making a call-by-call play, but I realize that some people do.