To be honest, I cannot tell wether I like the idea of a black market or not. On the one hand being able to buy stuff with gold would be useful, but on the other hand the value of gold has already increased by a LOT since the guild EXP update. I barely go offline now without throwing all of my money into the guild.
I think there are plenty of possibilities to spend your gold in a useful way. In addition, the arsenal allows you to buy all kinds of stuff so I think adding a 'black market' would be a little too much. Of course, in the end it depends on how this would be implemented.
Btw, this idea has also been suggested years ago.
- Somewhere likes this