You need some malt to help convert the sugars out of the wheat. From the Beersmith site:
Wheat lacks key nutrients and enzymes needed for proper conversion of sugars during mashing, so malted wheat is always combined with barley malt to provide enzymes for mashing and fermentation, often at a mix of between 40 and 60% wheat.
Some people have had success using a combination of malted wheat and unmalted wheat. I dunno... But, I think more importantly, there are enough rice hulls in the world to make my MLT do an only wheat brew. I'd have a stuck sparge for sure.