[Hall of Famer]

This sounds interesting. I heard you were working on a custom theme too? Hope it works out for you.

I see you are an ambitious coder, but even so I do not recommend a battle system at this point of your site development. Sure its completely possible for a professional coder to script a battle system in a few days, but there are a lot more stuff you will have to work out first. Stats sure are important(I assume you already know what to do with your own stats system, so I wont explain much), other mechanisms such as elements, status ailment, attacks/magic, equipment and battle items will take a while to design too. You will possibly need a detailed outline of what a battle system you want it to be before proceeding further. Ignore my words if you do have everything in mind already, those are just my advices for you. For me, I'd rather check if my site has everything I need before brainstorming a possible battle system.