Ok I'll try to answer all your questios:
250g ball makes approximately a 30 cm diameter pizza (or about 12"). yes you will have just a lit a bit of dough left.
The "recipe" is for a litre of water but it is an indicator for mixing as little as half litre (less then a pint) up to 50 litres and the total fermentation/maturation time stays the same..
Mixing less then half litre it is not convenient as it would involve measuring too small ammount of ingredients, and what you suggest by mixing only paniello, is not reasonable in my opinion. I understand that making pizza at home doesn't require mixing large quantities, but I believe that mixing at least 1/2 litre it is ok as it resoults in at least 5 pizza or you could make fantastic bread rolls out of the remaining dough.
Regarding the Istant dry yeast, I don't really have something against it, but when use it in very small quantities, the normal 1/3 ratio is not really true and you have to learn the differences. It sometimes act slower then fresh yeast and this may be an advantage. However I don't usually use it, as I do not think it is convenient measuring 0.8g per litre when mixing a small batch. If I had to mix at least 10 litres or more then I would consider it.
I have use IDY few times for small batches, and what I did was approximatelly dividing a 7g (available in UK) bag in 10 portions and use 1 portion per litre. The problem is that the remaining yeast would not keep for long, and in the following usage it would not act as the first time. You can still obtain the Crisceto from Sourdough International and have a better try, as it is easier to measure 25g per half litre .
Using a too cold water is not positive as it does not help to form a good gluten. My dough never even see the refrigerator.
It is all done at room temperature, just by controlling the cold and hot spots in the pizzeria and/or home.
I appreciate your offer, and I would happily have you in my team, but I do not think you would move to London (UK) just to work for me. However there is a possibility of me moving to US for a very good project I was recently been ask to be part of.
I don't know any famous pizza house in italy using a biga. I know few people in the north of Italy using poolish for a different product then pizza napoletana. The Caputo pizzeria is studied to produce the best results with the direct method as it as a medium/low enzymatic activity and it is a flour of medium strenght (w240-260).
I do have an insight of the best Pizza Houses in Naples, the one serving 850-1200 pizzas a day, and I will reveal some of this insight in my book. What I can tell you, is that the really good places still use only direct method, slow fermentation at room temperature, and a very wet dough.
I found this helpful..(quoted from one of Marco's first posts on this board.)