How about a simple tooltip mod, that lets you set the values of different stats, then shows a sum value for each item, making item comparison fast and easy, for any class?
That way, if a patch changes the value of Agi, I can just change it's weight, and get the right stuffs ^^
Just a simple "Rating: XXXX" in the item tooltip, and a settingsthing in Blizz's interface options where you set the weights.
(There are mods that show you stuff, but afaik none you can set the weights yourself? And they're often filled with other things I have no use for.)
/edit: Oh, and maybe have a toggle for gems/enchants like RB ^^