I think the bazaar could use some extra filtering to help better find the items you're looking for. Currently, when looking for gear, you can filter by usability, and then sort by alphabetic, level, school, etc. However, I think this can be improved.
Right from the get-go, I think a huge (yet simple) improvement would be the ability to check "usable" BEFORE the items start to load when you first open the bazaar. You can choose your category of gear before the items load, but can't check usability until everything loads.
As far as actually adding features, I think the bazaar could use its own filtering system, at least for the gear section. You could open a menu where you could select the school(s), level (or level range), and price range that you're looking for. For example, you could use the filtering to only display Storm gear in your chosen category between levels 10 and 20, with a price range of 1,000 gold and below (Additionally, you could set fields to "Any" or something, if you don't want to filter a certain category, such as price). It could be useful, especially if you're looking for gear to trade to another wizard with less gold on your account.