I have played a total of close to 1000 turns on the 'river merge' branch last week (at least 'Conquistador' level). Overall, this is
exceptional modding work, and I genuinely think that WTP has become one of the best 4x available.
A few points of feedback:
1) The AI currently uses scouts without a doubt; however, looking back, it did feel very easy (maybe easier than before?) to consistently get first native visits and goodie huts. This is difficult to test, and I hesitate to call it a 'bug' yet, since I am so aggressive with scouting and expect to pull ahead on that front; I will keep an eye out for this specifically in the future.
2) Large rivers are a great addition. In the 16th and 17th century, rivers were absolutely central to travel and trade (as recently covered by LindyBeige) , and having major rivers have palpable gameplay effects makes the map come to life. My only suggestion is to have not only enormous rivers like the Mississippi or the Amazon count as 'large rivers', but also have smaller, yet still very important navigable waterways count (thinking like the Hudson, Rio Grande, Colorado ). The end goal would be that each map have several 'large rivers' distributed throughout for balance and fun.
3) Speaking of large river balance, they may currently provide too much food. Food isn't that big a bottleneck to growth in WTP, but it might be still worth dialing down the bonus by 1 anyhow.
4) I have not encountered major bugs, after several hours of gameplay. It is almost a little sad for a beta tester to not have anything broken to report
5) The new rewards from goodie huts are fun, but maybe make exploration too strong. In particular, finding free units on the map might be too strong in the early game (I also feel that way about the free caravels). On a couple occasions, I rapidly encountered a couple free rangers, and was able to bumrush the AI without much difficulty. I think an OK middleground would be for unarmed veterans (and perhaps other precious specialists, like blacksmiths and preachers, or even generals!) to spawn in goodie huts. A different approach might be to give rangers and native mercs a penalty when defending or attacking cities (since presumably, they are smaller units of light infantry, which rely on stealth and knowledge of terrain to defeat larger formations).
6) The new trade quests are fun, but they can be hard to all keep track of. It can be difficult to know which resource to prioritize without knowing how close the AI is to achieving each objective. I have not yet pulled the commit with the increased resource requirements (looks like 500 -> 5000 for most resources based on the commit. Pretty drastic!), and so maybe this feedback is already outdated.
Some thoughts on modding:
a) Adding the DLL to the Github repo might be a way to make this mod branch more accessible to other users, although I understand if the modders would prefer gatekeeping access for the time being. Perhaps an install guide might be a helpful middle ground (basically just instruct users to install Perl, download the compiling tools from the repo, and run the .bat to compile the DLL)
b) A modding guide letting us newbies know 'where' to look in the code to contribute specific changes would be helpful (perhaps one exists already), maybe even broken down by programming language and/or difficulty (XML, Python, C++). I would love to contribute when I get the chance, and specifically could get started on easier components like quests and balance. For instance I think it could be really fun to use the new event system to add interactions between Europe and the colonies, to prevent early player snowball, and further bring the world to life (e.g. on colony capture: 'your king says to stop killing the French for now, but here's a reward for putting them in their place). Another feature I'd like to add would a simple checkbox in the trade menu to toggle imports of all 'luxury goods' up to 50 units, in order to more easily set up the internal market. I could try this out reasonably soon if I knew where to look