the traders never really bring that much of what you ask for
in that regards, I hope a finer control over requests quantity will be added in (influencing prices, of course).
Alternatively, the ability to have this sort of conversation:
Urist McTrader: "We want unbelievable amounts of flux stone."
Kogan McMerchant: "We'll pack as much as we can onto our next visit with 5 pack animals."
Urist McTrader: "Can you make that 50 pack animals?"
Kogan McMerchant: "Let's discuss advance payment for the risk we'll be undertaking to move with such a huge load."
Urist McTrader: "We have 30 tonnes of stone mechanisms to pay you with."
Kogan McMerchant: "Are you kidding? We can't carry that much weight!"
Urist McTrader: "Ok then how about this steel serrated disc with every gem known to dwarfkind encrusted on it and further decorated with goblin bones, bands of gold and rings of electrum?"
Kogan McMerchant: "I'm not sure we can find a buyer for that back at Mountainhomes. The nobles are having a hard time financially at present."
Urist McTrader: "Alright, suggest something then."
Kogan McMerchant: "I happen to know the mining guild at Mountainhomes is short on picks. Can you arrange for 100 iron picks of fine quality or better to be made before we leave?"
Urist McTrader: "Why yes, our legendary weaponsmith can whip those up and our 20 smelters have already prepared the 100 iron bars this'll need."
Kogan McMerchant: "You got 13 days before we leave."