I guess I should have filed this under "all grain". More attenuative yeast is the obvious answer especially posted under "yeast and fermentation ". How would one mash to achieve a wort that is 100% fermentable with no long chain sugars?
I'm not sure that it is practically possible. The alpha amylase will leave behind one fermentable bit and one less fermentable bit. The Beta amylase will nibble off the end of the less fermentable bit but still leave a less fermentable bit behind.
The molecules that each enzyme is looking for, once the enzyme has acted on it, will always leave behind an unfermentable bit (This is based on my limited understanding of amylase activity and perhaps others can correct/confirm my thoughts).
There are likely other enzymes one could ADD to the mash to increase fermentability though.