OK, I'll add some requests here, too
functions to identify tooltip data
A function to tell what kind of data is shown in a tooltip (unit, spell, item, 100% custom) and another function to get further information eg a link to the item shown. This would reduce the amount o hooked function wrt toooltips significantly and would also give as the oportunity to make sure all tooltips are catched. Currently this can only be done by matching the tooltips first line against a list of known items that has to be localized :/
more unlocalized values
having more functions returning non localized data that can be localized with other functions would give addon authors better ways to make their addons compatible with other language versions without having to worry about the exact terms used in localization.