well the point of a Free Trading fief actually would be that noone would need to ask.
As there is also already 20+% taxes on any transaction within Tismir, you always make a profit no matter who is using the S&D.
If you want to use it yourself to sell either you need to have patience
Conquisitore
or approach me and we can do a separrated deal over Khudan S&D which but would be an exception to the rule as we mostly need that ourselves.
Also you could increase the taxes upto 25% maximum, which then over time would net you a bigger general income, but i would advice not to, but increase the prosperity so that more goods could be sold there and you have the same effect.