Lord Elpus said:One of the biggest problems with Brets is that you can't really have anything big an monstrous with them
Unless they were linked to a caster, similarly to the way that a Slaughterbrute is linked to a WoC character. I will return to this in a minute.
As Adam_Barrow mentioned earlier, Bretonnian lore is rich in spirits and ghosts - I think an ethereal knight unit(s maybe, mounted and unmounted? Knightly Spirits of some description?) would be great, perhaps lead by the Green Knight. Games workshop have never been afraid to rewrite fluff to fit new models. Necrons were almost totally rewritten and the number of units increased almost double-fold. Brets are slightly more established than Necrons but many concepts talked about here would be easy to fit in.
Now monster wise, how about elementals, spirits linked to a specific caster animating earth and air (Bret magic at the moment) - perhaps with a water element only available to Lady of the lake (unless their own lore is water based??). If the caster dies they are unbound and lose form. I think that these keep within the spirit of Bretonnia.
Overall, I think that GW should be creative enough to make a number of new Bret units, keeping a strong Bretonnian theme and there should be no need to write Brets as an Empire supplement. I believe that the following for Brets is there, and sales of Bret figures are limited because the range and variation of army is limited. Indeed echoing many people thoughts here it would be tragic should this come to pass and we lose the unique Bretonnian identity. We can only wait and watch for GW's plan for Brets to unfold...