Why w and not v? some countries down.. Slovak and Czech Republic use v and they dont have single word with W so why do polish have everywhere W?
Germans also use w for v, and v is pronounced mostly as f (as in vogel) in German
i have some idea why it w was chosen over v - not sure if it bears any veracity though - in old manuscripts and letter carvings V was often used to mark U sound - have a look at some medieval tombstones - (at least when capitals were used) so I guess it was used as a disambiguity means
as for sz, cz, dz, dź, dż digraphs - it is a matter of tradition - if you adopted some system it is sometimes counterproductive to overturn it for another
well as far as I know Czech does use y sign and sometimes the sound of it is a bit different to i sounds (well I am not quite sure about it)
btw sz cz groups are unpronouncable in Polish, rz is though and there is a couple of words that have rz that is not pronounced as ż but as two seperate sounds (for example marznąć, mirza but marzyć has rz=ż)
maybe it sounds weird to you but this is the way this words (magazyn etc) are spoken in Polish (we after all have a distinct sound of y not quite similar to i - so do the Russians btw) - these words were polonised this way long ago they sound better this way in Polish - btw if magazin was spoken as native word you wouldn't recognise it in speech actually - magazyn can be picked up more easily I guess by foreigners
there are no native Polish words that use v (v sign is called fau following German lines)