Myth-Weavers - Combat System.

Hi guys,
I was wondering how one might go about designing a battle system. I have an rp I'm planning to do, but in anticipating people abusing their charas, I need a system and a way for it to be fair in the event it involves PvP, as well as fighting minions and whatnot. Trying to apply DnD or Pathfinder rules have proven too clunky--and admittedly, I'm still a rookie GM there.

I'm thinking it WOULD involve leveling up, still, but I'd like to take a lot of the guesswork out of it. It works like this, the weapons are typically going to be swords and the like--as it's pirate themed. Some guns and steampunk-esque tech. It would also involve ship battles.

What I'd hope for is some kind of stat rating system for how they've trained themselves, maybe? And a way for them to improve a stat if that's what they decide to do. Like, if they lift weights, after so many weight lifts, they gain a stat point? Or if they do speed training or regular sparring, etc. But maybe a fatigue meter so to keep how much they can train to some level of realism. XDD

*Ahem* Sorry, getting ahead of myself. Mainly, the gross would be weapons vs hand-to-hand, or if fighting monsters and ship to ship battles. If anyone has ANY ideas how I could get started on such an undertaking, I'd be truly grateful.