I agree with John from the point of view of digging a style out of the graveyard... it's definitely challenging (potentially impossible) and maybe not even interesting (except for those who enjoy beer-cheology, but that's likely a pretty small niche). In the Nederlands they are trying to revive gruits and other traditional beers (all-oats hopped beers, for example, which seemed to be the standard in the early 14th century) and they do have a few examples commercially available, but are those interesting past the "study" phase? Meh...