So I´m on a pretty lucky Venice game (managed to grab quite some land, from ottos too before 1500), and I ask if I should bother with that feature. Looks like a waste of slot for vassals or allies.
The trade league as a whole use up one relation slot.Trade league members don't use a relationship slot. Each member of your trade league gives you 2.5% trade steering bonus that stacks, and you get 50% of their trade power. More trade power also generates more goods produced in the nodes you control, which means more ducats overall.
Is it worth giving up your provinces to create trade cities? Not really. But if there are tags that willingly join then yes it's definitely worth it, especially if they are downstream from you and can help send more trade to your capital.
Ah, fair enough. Thank you for the correction!The trade league as a whole use up one relation slot.