Battles&Balances
Missing elements

There is much these rules don't take into account, mostly because they don't feature in any of my games yet:

I also haven't discussed darkness, light sources and visibility. Should probably add that in a future edition. (Dual-wielding torches for the win!) In the mean time, feel free to make up your own. Just consider whether additional rules make the game more fun, or just bog things down. Even with a computer handling dice rolls and math, it's still the player who has to take the various factors into account when making decisions. Moreover, NPCs also require AI, and that means more complicated coding the more rules you have.

Last but not least, we need to talk about setting, because generic rule systems aren't. Battles&Balances for instance favors games with a single character (as opposed to party-based) and carefully planned progression; this determines the kind of adventure it fits well. So far it's been used in several roguelikes and one gamebook, all generic dungeon crawls. From there to a compelling backdrop and story is a long way. Not that story has to mean an epic saga, but that's a whole other story. No pun intended.

Either way, make games you love and your players will love them too.