Obviously we dont know how trade work (if there is any), but I'm assuming it would be somewhat similar to EL.

 If so I hope we can be able to build special Trading outpost in other culture territory (or simple one with similar effect). This would allow to extend trade route to make them giving more money (and maybe spreading some influence). Each territory would be limited to 1 trading one and you can't build them if you already have a city or regular outpost in it.

The cost would be that you have to give a x% of the trade income to the owner of the territory, and that the outpost can't be builded everywhere (only border?) and/or need to have a special treaty allowing you to have on in a specific territory (so you could do a diplomatic deal to have 1 trading post in this territory = concessions, but in exchange giving the owner X% of the benefits + a tech help treaty for example, or done after a war or threat, like opium war)

These concession might be for X turn, after you can reconduct/adjust the terms or try to keep it, if so you are exposing youself to be declared war upon by the owner, or that they can freely burn the outpost but giving you the ability to declare war against them with better reason (cost less influence if works like EL or ES)

This would allow to simulate the various trading outposts in colonized territory that happened in lot of places : portuguese in africa, french and brits in india, hong kong, dutch in japan ans so on; or even modern companies have subcompanies abroad

The number could be limited to a few per player and merchant culture would either be the only one be able to build some, be able to mantain more or better one

Maybe they could have a few upgrade allowing to store navies in it, spread better religion and influence, make more money or fortify

+1
an embassy would also be a nice addition to that