I know some addons like RatingBuster shows itemlevel in the tooltip, but this is the itemlevel as given by the server/whatever, would it be possible to have an addon calculate the actual itemlevel of an item based on its stats?
Mendeelev can show these numbers, it can also show a lot of aditional information about items in the tooltip. The version in the trunk uses an old library wich is not up to date for the TBC items (does work though). However this version should be good enough for showing item levels.
Even if it wasn't completely accurate, I'd like to see this just as a comparison. So many items are itemized wrong (using the old stamina cost, for instance, is rampant) that it'd be a nice summary of what was done poorly (bad choice of stats) compared to what was just done wrong (not enough stats).