This Trading Post improvement is still in Patch 2. Already done.
The fort has to be on the flat surface and have your culture. One cannot sail into hills.
Antigenes: this improvement is available with a certain tech AND it can only be build on a legal resource! Forts can be built anywhere.
Just wanted to report a couple more bugs: first is a CtD that I can't always reproduce, but happens when I move the mouse cursor towards the lower left corner of the screen. This has been happening since PAE IV, and isn't consistent so often reloading from a save is fine. But it has now happened twice in the past hour or so. I can't tell what icon or unit is triggering the problem either.
Second: you can see in this screenshot that all the Illyrian cities in my game don't have proper names, but instead have what appears to be a bit of coding. Hope this one is easier to fix.
1) commissioned mercs: with 4 elite units works well, but with 8 elite... with have a stack of 16. I think with 12 will have the same, 16 units.
2) rice and progation: it's impossible. PAE concepts says: flood and grassland. I had grassland (9 tiles) and 1 with flood, and I could not. More: I havent seen any flood+grassland, only with WB. There are desert+flood or grassland+swamp. Maps generator dont create any grassland+flood. I have seen that flood can propagate like a forest, but this is very very very uncommon. A lot of luck we need.
2) rice: hm, that's true. where should I provide rice then? a wet and warm climate is necessary. perhaps a grass tile with river and a jungle near the city.