Armor in the campaign.

This isn't a complaint about RPG rules themselves.  My concern is more with the settings presented in many sourcebooks, or the implied setting in certain games.  It may be nice to have rules for all sorts of armor, but characters shouldn't have free reign to purchase any type of armor that was ever invented if you want to have a more realistic campaign.  There should be a few option available, based on what is locally available and currently made.

Using 1e as an example, Gary lists the following type of armor:
Banded
Chain
Leather
Padded
Plate Mail
Plate armor (full plate)
Ring Mail
Scale Mail
Splint Mail
Studded Leather

There has been some debate as to what types of actual armor these categories represent.  What exactly is "Banded Mail"?  Is it the classic roman lorica segmentata?  What about "Splint Mail" and "Ring Mail"?  Regardless, after some thought it would seem to me that this list is composed of various types of historical armor that was used in Europe and the near east over 1500 year period.  To me, the idea of a character being able to pick his armor out of this entire list seems fairly absurd once I really thought about it.

I was going to go on to say something about how silly it is for a character in a D&D game to be able to pick between 15th century style platemail and 11th century chainmail.  If plate existed, everyone would be using some form of that.  But I always go back to same winning argument that was made in a comic book store long ago: "It's a FANTASY game!"  So really anything could happen in your campaign, but I just wanted to mention it if you felt you wanted to run something with a little more historical accuracy, and to point out how Gygax might have gone a little overboard with the armor listings, though not nearly as bad as he did with polearms.

In the long run, it doesn't really matter what the armor looks like.  The particular construction of the armor is only really important if you want to use things like hit locations and to hit adjustments based on weapon vs. armor matchups.  As far as I am concerned, AC 5 armor could be chainmail, or it could be poorly made plate or very well made and thickened leather.  If you don't use hit locations then AC 5 might be plate without the helmet and greaves (I think 3e already does this sort of thing with the breastplate and chain shirt armor type).

I also began thinking about different sorts of armor that might be made out of the various monsters that are found in the game.  To my mind, we don't see that sort of thing enough in D&D.  Sure, from time to time you see things about making armor out of dragon scales, but what about giant insect carapaces?  I think Dark Sun had some rules for things like that, and it certainly adds some flavor to the game, and really that's what I'm aiming for.  Simple rules, lots of flavor.  That's the difference between Old School and 3e-4e.  In the new systems all the flavor is in the rules.  In Old School the flavor is in the fluff, and that's always easier to work with.