(First of all, for those who don't know E6: here

I had this thought, if I remember correctly, while I was walking out of Barnes and Noble tonight. An absolutely outstanding application of the E6 mechanics would be to the Birthright setting.

First of all, you've got several ways your characters can grow; via feats from the E6 growth, and via bloodline strength, and via political strength. The world itself already assumes a much lower level of magical strength than is common in standard D&D campaigns, so capping it at E6 levels isn't that much of a stretch. For Magicians, bar them from EVERYTHING but Divination and Illusion, but throw in Shadow Evocation and Conjuration at level 3 illusion spells (mimicking 1st-3rd level spells of the Evocation or Conjuration schools, respectively). Bards could maintain their own spell lists, but properly pare them down to enchantments, illusions, and divinations ONLY. Only Sorcerers (using their elven or deific heritage) would be able to be full arcane casters; make additional spell knowledge a blood ability, perhaps, open to Vorynn's and, of course, Azrai's, line (in addition to being an E6 feat). This preserves some of the uniqueness of Magicians as prepared casters, but also allows Sorcerers to harness their blood to get ahead.

A human power level, ritual magic as part of the background, unique monsters...The setting almost seems like it was BEGGING for E6 to come along.