I was assuming you'd want to make a conservative estimate of people's playing abilities. Someone who's only played clarinet or trombone in a Dixieland or military band won't have used a wide range of keys. Once you know the players better you can ask for more.

But if you want confident virtuosic flourishes it would still be better to keep the tonality conservative. Example of where that is *not* done: the Janacek Sinfonietta, which is mostly in A flat minor, but you need to pay for serious amounts of rehearsal time to make it work. It has probably the toughest flute solo in the orchestral repertoire.