Some thoughts on upgrading the inventory (in no particular order):
Weight limit should be fairly easy to automate.
Likewise encumbrance, maybe tied in with effects or the wounds modifier star on the mini sheet.
Drag and Drop gear.
When a weapon is dragged to the weapon pane it auto adds in the inventory and vice versa (as in latest 3.5e).
Number off items and base weight to give total weight.
Support for decimals (not sure if we have this or not?)