Milquetoast

Lorenzo is right on both accounts; you don't need a full arming cap or anything terribly thick, a balaclava would work fine, just so the maille isn't directly against the skin, and their welded maille would be your best bet for safety. But I have to voice concern over your game: please correct me if I'm wrong, but it's sounding like you're wanting to do a backyard sort of game with some friends, which if you've browsed airsoft forums I'm sure you've seen advised against. It's too easy for a neighbor or passerby to see you and call the police which is a hassle even if you're legally fine to be playing, or to get a bad article written in the paper (because airsoft is definitely weird to most outsiders), or the most important factor, it's very easy for someone to get injured because oftentimes backyard games don't have the same safety regulations as established groups/fields. I would definitely recommend that you spend some time with a local group and do a few real events to learn what the common rules are and why they're in place, if for no other reason than to make your own better.

I stopped airsofting 4 or 5 years ago, but I wore my maille once, so I can give you a little bit of insight. A few questions first, since I did field, not CQB: I'd always seemed to hear that the FPS limit was 350 with 0.2g BBs, is this true for where you play? Do head shots count as hits where you play; that is to say, how likely are you to get shot in the head and/or face? I know that at my field we didn't count hits to the head just to discourage people from unloading on peoples' faces and risking chipped teeth, bruised ears and damaging some of the thinner skin, but I don't think that it's a common rule. One thing to remember is that once the BBs start to lose velocity, they lose it fast: that's why even relatively thin clothing is fairly effective at preventing the BBs from stinging if they're loose and away from the body: tight clothes will just transfer the force of the BB straight through, while loose clothing makes it necessary for the BB to pull the fabric with it to get to your body, which sucks up a lot of its power. Maille is the same way: a weave that's sitting straight against your noggin will transfer most of the force through, while if if has to move the maille a distance, that will use a tremendous amount of its velocity, so you'll want some way to keep it away from your head (such as a cap of some sort).

I turn bronze into a nice deep brownish-orange within a few days, sometimes even just a few hours if I'm sweating, but I have 0 problems with ever getting the green rub-off. It's really something that varies person to person: I personally love using both bronze and brass, I love the rich, deep look that they get when they've tarnished: I just make sure that before I make a piece for someone they know about the possibility of greening.

I've had rings sent to Illinois, Florida, and Michigan without ever being charged any extra fees.

18g 5/32" is my favourite Byzantine size, or anything around a 3.5 AR: much bigger than that and it gets pretty loose and floppy until about AR 4.2 when you can stick a third ring in the little "boxes." CGMaille-- http://cgmaille.com/tutorials.shtml --is always the site I recommend for beginners to jewellery: it's got info on enough weaves to keep you busy for quite a while, and some of the best, most clear tutorials I've seen.

What's it from, by the way? I thought I'd seen just about every Medieval fantasy film out there, but I don't recognize this piece wherever it's from.

16g 5/16". The wire's definitely not thicker than that, and if the ring ID was any larger the weave would be much more loose and open.

I don't have the appropriate rings to check, but depending on how obvious it is, inserting an expansion in the middle of the tie where you want it to expand could work and keep the edges even. http://www.mailleartisans.org/articles/articledisplay.php?key=495

The Armour Archive is the place to go for all things SCA: if you check over in their Classifieds section basic knees and elbows can usually be found for pretty darn cheap. And if you really want to have a go at making them yourself rather than buying, they've got a lot more smiths over there than on this forum that could give you direction.

They're definitely not TRL scales so you won't get the same flat, angular look, but size-wise they look to be roughly near to the large scales. I've been planning a scale Kingsguard hauberk like they're described in the books, this reminds me that I should start that soon...

If you can get all of your rigid armour requirements taken care of elsewise, 16g 1/4" and 14g 3/8" are good SCA sizes: they'll hold up reasonably well for being butted (but will require regular repair), without getting into the realm of extraordinarily heavy

How big will it be? My own personal dice bag is 18g 3/16" and holds two sets of D&D dice (as many as I ever bring to a session), but some people like theirs to hold all of their dice at once, which for some people is 50 dice, then 16g 5/16" would work alright. It's a matter of scale: making a small bag out of large rings will end up seeming very loose and floppy and coarse, while if the bag is large then larger rings work okay.

What weave?

My scale shirt used 14g 5/16" steel up near the top (over the shoulders down to about armpit level) and 16g for the rest. I'm not sure just how necessary it is for the costume wear I use it for, but I've never had to make any repairs so I guess it doesn't hurt.