Thank you for the encouragements!
I still keep all the files, so...
I have to break it, though I hate to admit this - there were some major challenges, which were never quite overcome in this scenario.
The first was the huge map, which nearly took my breath away to set up. The trouble was, however, how to direct the AI on such a huge map, to make it just the least bit historical. As a solution I ended up removing large parts of the map, sketching out the route to make things more scripted. But I was never satisfied with the result.
If/when I do take it up again, I will have to make a smaller map (a la the Hammer map, which is still quite decently sized), which will make AI action much more contained, and the player struggle much more intense.
The second challenge was the tech tree. I never found a satisfactory solution for how to use it. On the one hand, its a period with a lot of obvious "white man's technology" to construct a traditional civ2 tech tree. On the other hand, I wanted to show the deterioration of all "white mens ideals" such as Progress, Science, Enlightenment etc. in the face of 'darkest Africa'. I'm sure there's a solution, I just never got it quite right in my head - and eventually it just came stuck.
I will probably end up doing a somewhat traditional industrial tech tree - as it is what I do best, and what civ2 is best set up for. This lets the game speak for itself. What does it matter if you have "steam engines" when in the middle of the jungle, surrounded by hostile cannibals?
