Add some Brett.
+1 I think that without some very specialized yeast there will always be some longer chain sugars that will not ferment out. By the way are you talking about 100% Apparent Attenuation? ie. a finished gravity of 1.000? I've done that with the belle saison but I added some honey.
100% true attenuation would land you below 1. How much below would depend on the worts starting gravity