What is excessive crosswind?
ATC can not nominate a runway for use when crosswind exceeds 20kts if there is a more suitable runway... thats the rule in the ATC Manual of Air Traffic Services and echoed in the pilot bible...AIP. Some years ago, for noise abatement issues (read politics) Sydney was permitted to nominate a more noise suitable runway with up to 25 kts of crosswind... I believe this exception was removed after industry pressure. Nothing prevents a pilot from requesting a runway that ATC may not nominate BUT such a movement has potential to create major hassles in an already complex situation and may not improve the movement rate at all.
Eg an aircraft which, for traffic management reasons, ATC would prefer off 06 is given a 20 min taxy delay. Pilot says, we'll accept RWY 03 if you give us an earlier slot. This would on the face of it seem to have potential to up the departure rate but it is just as likely to create more problems.
Fact is for traffic segregation / efficiency reasons we actually want only certain the aircraft to depart from RWY 03 (BIU5 and BINDI8 SIDS). Flights departing to the east from RWY 03 are a pain in the proverbial when trying to process departures from RWY 06.... Ah 'tis a complicated business 'tis!!! Visits by pilots always welcome and appreciated, call us on phone to make arrangements... obviously the word is out about the customary chocolate cake fee! donuts are ok too, free coffee in return.