In AORP, Saint Ehlers takes full responsibility for levelling characters and so forth. But he also offers the option to players who want to level their own characters.
I'd suggest letting the GM have full access to the sheets of any character in the game, and letting him lock or unlock the character sheets for their owners at will.
Though as Spriggan said, I'd leave the inventory up to the player. Inventory is going to change frequently anyway, and it would be a pain for the GM to have to update that all the time.
If you wanted to get really fancy, though, one thing that might be kind of cool is for players to have to specify where/when their char got a particular item. You could use a separate table just for inventory, which would have four columns: Owner Character ID, Item, Justification (Why the player has this item), and Equipped (Yes/No). Optionally you could also include item weight. Since inventory/equipment is pretty universal, I dont think it needs to be associated with a particular system at all. If this is unclear feel free to ask for clarification.
A text box for equipment would be just fine too, of course. But theres always the possibility that players might feel inclined to be sneaky and add inventory items. Then again, the GM is likely to remember that the player did not recently acquire a particular magic item.