A319/A320/A321
Limit for T/O and Manual Landing: 30 kts
Max Demonstrated: 33 kts Landing / 29 kts Takeoff (Airbus Logic)
Having flown the BAe146 before, I think 40 kts cross is basically managable, depending on aircraft control behaviour, in the SIM we once did almost 50 knots (steady) without any problems.
However 40 kts steady wont be seen too often, and even if so local topography may bring very nasty turbulence just over the RWY, so I think you'll be flirting with leaving the runway sooner or later. Ad some gusts and here we go.
Do that on the 5th sector, afer 12 hrs, after a non-precision app in the dark with rain. Good Luck.
In my opinion, limits should be set so as to reflect the average company pilots skill at any time. It's unfair to raise them and after something is broken or bend to ask the Commander, why he hasn't pulled the plug in time. How often do you experience 40 lts cross or train for it?
As fas as max demonstrated values are published, I wouldn't dare to operate outside them (except in Emergency). I'm no testpilot...
Regards, MAX