The lack of trees is making my eyes bleed.
Oh and Jomini, there were people in the Great Basin during the EU era. What in the hell are you on about? The reason there was little movement of Americans into the region has nothing to do with it being "inhospitable" and everything to do with it being a long god damned way from Virginia.
Foul language removed - Seelmeister
It had everything to do with being inhospitable to the people modeled in EU as settled provinces. Being a long way away from Virginia
makes it inhospitable to the sorts of people who could raise musketeers by the thousand (let alone cannon). So you want to settle the picture shown above? Great that is a LOT of pine to cut down and extremely irregular terrain you will need to terrace. That means you are going to go through rough iron saw bands and ax heads quickly. Just punching a road through there with 18th century tools would take forever. You could try the New England method for clearing trees, but burning off the forest cover in the Rockies is a phenomenally good recipe for flash floods and disasters. After all, you don't have established population centers with the specialized craftsmen with which you need to have some trade linkages (yeah you might import a blacksmith, but making a good anvil is something only a few cities on the Eastern Seaboard could manage. So you need a way get something valuable to the Eastern Seaboard to pay for your anvil and a way to get it back cheaply enough to be viable. That just doesn't exist for the Great Basin in 1820. If you want to raise up 1,000 men with guns, well you need a lot of downstream tool production for that mass production of firearms. None of it existed in the Great Basin until after the Civil War.
As a soldier, looking at your picture shows a great example of terrain that would be impassible to an 18th century army. You have no space for wagons between the trees. Well great, you can send out pioneers to cut a road through ... well no if you look at the topography in the picture you see a lot of steep descents with soft soil - this will eat wagons with ease and a thousand marching men will churn the ground into terrible marching conditions. Trying to get cannon through that? Well you need to lay down McAdam roads. Laying down those roads - that requires a LOT of tools. Likewise the terrain is conifer - so you don't have good sugar sources for anywhere near enough meat to make a dint in the provision quantities an army needs.
Again when people actually made the trek from Winter Quarters (having gotten that far via steamboat which is outside of game period) to Salt Lake City they took hundreds of pounds of flour per person - because they weren't stupid and didn't want to die on the trek.
Again is the Great Basin is so hospitable - why did The Army of the West, detour hundreds of miles south from Leavenworth, ride the Gila, and then invade California from the south? It is a straight shot across the Great Basin from Leavenworth to California and the orders were to march on California ASAP. So if it is so hospitable to transiting troops ... why did they go way the hell out of their way around it?
Set the base supply capacity to zero and add an attrition malus?
That turns it into an AI blackhole. You have two choices here then - have the AI ignore it. Well great, now the play can abuse the hell out of thing (hey I took 50% attrition, but I invaded the Eastern Seaboard from California - flanking the AI's army on the Gila - and now I can steal/burn the in progress colonies and hole up in the mountains. So if we want the AI to use it, we have to be VERY good at programming its cost/benefit analysis for exactly the sorts of things that AIs are piss poor at - anticipating human actions. Likewise, if the AI is running me down and I retreat through the zero supply capacity province does the AI follow or not? After all if I just have 5K to the AI's 50K, one pass through the blackhole kills more men than if I lose
everyone in the baiting.
As it stands the Sahara is depicted with utter retardation. Besides from being fugly on the map, historically there were a few dozen routes to take through if from oasis to oasis, but no, the Dev's chose to arbitrarily depict one grossly ugly route.
The Devs picked the one and only route actually used by an invading army in the time frame of the game. Provinces in EUIV let armies march through them. While their were trade routes through the Sahara, few of them could support anything close to an army. As crappy as the one shown is, it is actually among the more hospitable for sending an army through.
It's a strategy game, not a simulation game is the way I've made sense of it for myself. France and Great Britain also had trade settlements through the uncolonizable parts of Canada well before 1820 from what I understand. I can understand wasteland like the Sahara and the Himalayas, sort of. Great Basin is certainly one area I agree should be open to colonization.
Not every trading post had the potential to be a colony. For instance trade posts up the Frazer could work only for one type of good: Fur. The river has bad rapids or as it was described in period "I should consider the passage down, to be certain Death, in nine attempts out of Ten. I shall therefore no longer talk about it as a navigable stream". So you had a lot of portage to use the Fraser as a transit method ... however a few brave/foolhardy folks were out trapping furs in those areas. Fur had an
extremely high value/weight and value/bulk ratio so you might be able to send out small parties to trade with hunter-gatherers who lived in small sustainable numbers off the game in the area. Moving through 1,000 men at arms is going to completely destroy the regiment. Hence why the now included Oregon trail is historical BS. Moving people through that area takes more poundage per person than any army in the EU era ever carried or could have carried. Going down the Dalles was a one way trip for anything but the lightest of canoes; it wasn't until you had a lot of better tools from the 1830s onward that you could open a road around the Dalles that might, might let army through (the first attempts by the US Army to transit the path shown in game failed miserably -
decades after game end).
If a period army couldn't have made it through, then it shouldn't be open for colonization.