|from Matthäus Schwarz's Klaidungsbüchlein|
So, a minimal bit of googling yielded this page from the Metropolitan Museum of Art: Arms and Armor—Common Misconceptions and Frequently Asked Questions.
Here's a choice bit:
When early scholars of armor looked at medieval artworks, they noticed what they thought to be depictions of many different forms of armor: rings, chains, bands of rings, scales, small plates, etc. With poetic license, all early armor was referred to as "mail," distinguished only by its appearance, hence the terms "ring-mail," "chain-mail," "banded mail," "scale-mail," "plate-mail," and so forth. It is today commonly accepted, however, that most of these different depictions are actually various attempts by artists to efficiently show the surface of a type of armor that is difficult to render both in paint or sculpture. Rather than showing each interlinking ring, the small links were stylized by dots, slashes, S-shapes, circles, and the like, which readily lent themselves to misinterpretation.Obviously, there were a lot of historical variants on armor design, but I'm going to take that as validation for lumping all the mails into one category: Medium/Semi-Rigid.
Regarding mobility, the page makes the point that a suit of field armor (as opposed to tournament armor, which no one would go adventuring in) weighed about 50 lbs., and that this weight was well distributed across the body. This struck a cord with me. My brother is a cop, and he wears 50 pounds of equipment, mostly hanging off his belt. This is not an ideal distribution, and he can run, jump, climb, and, in at least one instance, tackle a guy on a tricycle.
...historical sources tell us of the famous French knight [...] who, in full armor, was able to climb up the underside of a ladder using only his hands. Furthermore, there are several illustrations from the Middle Ages and the Renaissance depicting men-at-arms, squires, or knights, all in full armor, mounting horses without help or instruments such as ladders or cranes. Modern experiments with genuine fifteenth- and sixteenth-century armor as well as with accurate copies have shown that even an untrained man in a properly fitted armor can mount and dismount a horse, sit or lie on the ground, get up again, run, and generally move his limbs freely and without discomfort.Fine. I still like the idea of restricting Heavy/Rigid armor to Fighters, but they won't have any restrictions placed upon them while wearing it.
Should Heavy/Rigid only be for Fighters (B/X = Human Fighters), or "fighter types?" I have no problems taking plate away from Halflings and Elves, but I feel a little more awkward about striping it from Dwarves. What are your thoughts?