The updating of the river systems is cool and makes sense, but one of the biggest things about this game is that it provides a truely realistic feel to it. I think that you should add a preferences/settings option for the biomes to be placed realistically, as the experience of “walking for days” to find different resources and biomes or animals can be really rewarding. Plus it encourages more playing hours, and gives another whole new way to play the game
Minecraft also has large biomes (which I normally play in) and the normal one.
I’ve traveled Europe a bit and I have to say, there are some quite boring landscapes. I don’t mean boring in an absolute sense but in a gameplay sense. The climate change with the respective plants is exactly the same if you go from the south-most point of Finland to the north-most point of Norway or if you hike for 2 hours from 1500 Meters above sea level to 2500 Meters above sea level in the Swiss Alps. Well, it’s not exactly the same, but surprisingly similar.
I would do something different. It’s probably not as game friendly as the final solution of Dave but its a bit more realistic. I would let the world generate realistically and only make spawnplaces for the sapiens at interesting points. Like at rivers, coastlines or ore-mines. You could improve the game, with a selection of spawn places like coast, river, lake, forest, planes, mountain, deserts, arctic… each coming with its individual play style. And after a while you have a developed enough civilization to go beyond your own landscape. That way it would make different staring locations (like the arctic) have different difficulty levels for building an empire compared to others (mediterranean coast).