I'm developing an indie game for mobile platforms, and part of the game involves a PvP battle system (where the target player is passive). My vision is simple: the active player can select a weapon/item, then attack/use, and display the calculated outcome. I have a concept for battle modifiers that affect stats to make it more interesting, but I'm not convinced the vision is complete.

I've received some inspiration from the game engine that powers Modern War/Kingdom Age/Crime City, but I want more control to make it more fun. In those games, you don't have the option to select weapons or use items, and the "battling" screen is simply 3D eye candy. Since this will be an indie game, I won't be spending $$$ on a team of professional 3D artists/animators, so my edge needs to be different.

How would you make a battle system like this more fun and engaging?