[jojobas]

Malting is harnessing natural enzymes produced in germination, better malting is a side effect of faster sprouting (something they'd plausibly breed it for). Wild barley is still around, one could hybridize as early a variety as he wishes. Lambic beers are still produced on wild yeast too.

It would be hard to match an exact beer as a particular early brewer made, but seemingly easy to cover the entire spectrum of beers plausibly open to them. Then again, I have doubts they were consistent and reproducible with the kind of instruments they had.

[KineticLensman]

I’d guess that individual brewers with years of experience could have produced remarkably consistent results and their apprentices would have picked up the skills. But every brewer would have produced different flavours. The weather conditions would have led to variations.

[jojobas]

Not from what I understood from working at a brewery. They would have to eyeball the brewing temperatures and fermentation temperatures would not be constant either, so both sugar initial wort sugar content and yeast-defived flavours would be all over the place.