DISCUSS: ELEMENTS

In general, I feel like it's sort of not good to come up with more "interesting" names for the same old elements. I understand the reasoning: it makes the thing feel slightly more unique and makes it stand out a bit from the Final Fantasy clones...
...but the thing is, the mechanics are almost always identical to begin with, though the amount of bonus damage might change. As such, using different names than the player is used to only serves to confuse them, rather than actually making the elements feel any different. Most players are probably still just going to refer to "Firmament" as "Air" because they're used to it (even though Firmament is an awesome word). If you're going to copy a system wholecloth, I'd say it's better to rely on the audience's familiarity with it as a starting point, and branch out from there if at all possible.

With a system as familiar as elements, I say strive to make it simple (not necessarily easy, but simple) for the player. Use logical and time-honored interrelations, like Water > Fire > Plant (Pokemon starters!), because there aren't many benefits to making it Earth <-> Fire. It'd only frustrate players and make them feel like you were trying to irritate them. Keep the number of elements relatively small. Four and Five might be traditional in the real world, but three is probably the number to shoot for here (RPS, remember?). Three elements means A -> B -> C -> A, which is the smallest and most elegant way of allowing a player to trump attacks, doesn't require the weird option of having an element be both strong against and weak against another element (Fire <-> Water is annoying.) and offers plenty of depth to gameplay if done right.

I like that collection of attributes, Craze, I just wouldn't describe it as an elements system to the player. I wouldn't even acknowledge the existence of attributes, actually, I'd just let the player know that different types of weapons deal different damage to the same monsters and be done with it. If there's a scan feature, beastiary or just NPCs who might tell about enemy weaknesses, that's cool, like "Our hunters who use boomerangs have the most luck against Cabbage Men," but with that many different things available I'd avoid asking the player to remember everything on their own. And item descriptions, of course, like you said. "Resists fangs" or whatever.

My main thrust is to make everything as transparent (and wherever possible, logical) to the player as possible so that playing the game is less about remembering the rules and more about figuring out new ways to exploit them.

While I do have elements in my game what's important is weighing the various advantages that each element(al style) gives, stat-wise, and the field advantage- rather than a type advantage over an enemy.
There's
-Fire
-Water
-Wind
-Nature (plants, wood)
-Ice
-Lightning (thunder and light)
-Gravity (rock, sand)
-Materia (poison and dark)

And they are strong and weak against each other like so:

Water > Fire > Ice > Water
Materia > Nature > Thunder > Materia
Wind > Gravity > Wind

Weapons and monsters, don't have elements- the only things that do are objects, items, and the player.
For instance with objects, there are some rocks that are on fire. Said rocks on fire damage you upon touch, but do much much more damage if you're Ice style, or do no damage if you're Water.
Then, once you get the water element item, you can douse the rocks and make them like not on fire. Yaystuff.