There's already been not
one but
two threads on the FTWD saison recipe, although that seems to assume access to a LHBS.
I think my comment on this thread would be that people are trying to do too much at once, it would be better to take individual parts of the problem and try to solve them separately using "good" ingredients for the other parts in any one beer.
For instance, here in the UK I know I can get (bottle-conditioned) Fuller's 1845 or Adnams minikegs in my local supermarket and I know that it also has sterile 1.050 sugar-water in the form of UHT apple juice, and yeast nutrient in the form of Marmite yeast extract. So in principle I could shake up some 1845 dregs and a dab of Marmite in a carton of UHT apple juice and know that it would work pretty well as a GaP starter culture. You could even mix juice/Marmite with gelatine to plate out yeast, using jam jar lids or something as Petri dishes. If we were in a zombie apocalypse and could flex the rules a tad, I could scavenge yeast from the empty casks at my local pub.
But I don't need to do all that for R&D purposes, I can use WLP002 as an interim measure which will be easier and more reliable whilst I work on more difficult aspects. As an aside - a lot of bread yeast is POF+, so makes phenolics like Belgian yeast, I'd trade one of my nubile slave girls in return for POF- yeast from eg bottle/cask dreg as it will mean better beer and more NSGs in the long run, if NSG numbers are your measure of success.
Malting/mashing is obviously the big problem. Beano is not a thing here, in fact I'm struggling to think where you could get any kind of enzymes off the top of my head. I like the banana idea, and surely potatoes must have huge amounts of amylase once they are chitted? I've also seen maize suggested as a good source of amylase. But the one I'd probably try first is (mung) bean sprouts, we literally eat malted beans, there must be a ton of enzymes in there.
But in the meantime, I know it is on the borderline between beer and "wine", I'd been thinking of using golden syrup as my fermentable with a dash of Marmite in it as yeast nutrient. Maybe boil pearl barley in it for barley taste, maybe some Scottish porridge oats for better mouthfeel.
We may not have Beano, but we do have anti-wind medication based on simet(h)icone, the active ingredient in Fermcap. So we can prevent boilovers, in fact even pre-zombies I use things like Deflatine as an alternative to Fermcap.
Water chemistry - the supermarket has citric acid, limescale cleaner, and I've been in supermarkets on the continent which sold eg hydrochoric acid. And there's always lemon juice and Coke for acidity adjustments... Keeping the pH down will help minimise tannin extraction from some of the weirder ingredients. Epsom salts and table salt are no problem, I'd have to go to the DIY shop/builders' merchants for building plaster, which is essentially impure gypsum, or (proper) Plaster of Paris which is the same stuff, dehydrated and a bit purer.
In the zombie scenario, I have access to wild hops and bog myrtle - a tea of the latter tastes surprisingly like an APA. But in GaP terms, I'd start looking for bitterness by using tonic water (preferably full-fat) as my brewing "water", and adjust bitterness adjustment using either
Sodastream tonic concentrate, or Angostura. I've had a beer with hops and quinine in it, it does work, and your beer is fluorescent!
For flavouring my "pale", I guess lemon/orange/grapefruit zest, maybe a teabag or two. For a dark - coffee beans, cocoa nibs, some home-toasted grains.
I didn't intend it but I guess that's ended up as quite a British take on the problem - golden syrup and Marmite dissolved in tonic water with pearl barley and porridge oats, fermented with Fuller's yeast and flavoured in part with a teabag. But localism is part of the story, right?