I would definitely love help on getting this developed. The combat system I have in mind is pretty simple. But I like a combat system because it makes sure combat plays out nicely with the intensity kept in tact and also provides something for players to work for (equipment, level up, new abilities, better stats). Often, with no guidelines for combat, I find that the writing becomes a ploy to make their character look like fuggin samurai jack against a thousand aku-bots xD

I was thinking combat could be ruled by a couple of simple statistics: 

Health: Amount of Dmg that can be sustained before KO
AP: Abilities points that can be spent on abilities 

Attack: Dmg you deal per attack
Speed: Number of attacks you have
Armor: Amount of Dmg absorbed
Reflex: Number of attacks you can dodge

Abilities: Special attacks that cost AP and SP in order to use.

I'll write up an example later. Right now we need more interest. 
And as far as what characters you can play, they can either be from the game, or entirely made up. I would provide the in game characters only as a platform for creation. For instance, the mercenary class, would have everything from the game(blade wielding, windmill slash, eviscerate, ect.,), however the gender and character background would be decided by whomever chooses the Mercenary. But you're more than free to play the lovable poisonous ooze leaking offensive to the olfactory Acrid xD