Screw coming up with an exacting universal system. Weapons have a damroll which is the specification of how to calculate how much damage it inflicts. This goes against a target's Defense roll, which is the sum of the defrolls of all armor and their base defense attribute. It should be possible to get both the attacker's and victim's full stats into the damage and defense rolls and perhaps various environmental conditions as well (e.g. fire magic is weakened by precipitation). Damage done is always attacker.damroll - victim.defroll.
Players have several base stats which are mostly based off of OSRIC: Strength, Dexterity, Constitution, Intelligence, Wisdom, Charisma, Divine Favor and Alignment.
The game is classless. A player's class is the sum of his skills.
There will be various Deities. Divine favor is accured based on various actions, much like alignment. Alignment is a secular attribute (i.e. whether you're good or bad according to social norms), while DF is based on the whims of the deity.