Why is "May you open the window" not correct? Of course normally it would include 'please', as in "May you please open the window", or "May you open the window, please".
wouldn't "could you open the window?" work as well? 'Could you open the window (please)?' sounds like a definite request; 'can you open the window?' could be a request or could be asking someone whether they're able to to open the window (umiesz)
but maybe "could you" is not really proper grammar, but people just use it. I'm not sure.
ah, I checked my Polish grammar book. I think "could you?" (sounding perhaps more polite, tentative in English) would translate as "mógłbyś" in Polish?
mógłbyś/ mogłabyś otworzyć okno? = could you open the window (please)?;
możesz otworzyć okno? = can you open the window? (request);
umiesz otworzyć okno? = can you open the window? (are you able to)
Well, this one is a lot less likely than usual, but of course technically it works - added.