Bethesda is well known for their massive open worlds and commitment to the idea of free-roaming. However, what makes them a serious contender for this list is the fact that they do factions better than most other studios. From the Dark Brotherhood to the Brotherhood of Steel, Bethesda's factions are brilliantly written and allow the player the opportunity to carve their name into the annals of their world.
If Bethesda sets its sights on a Western game, it would be safe to assume that they would find a way to incorporate myriad factions into it in order to provide the player with an incentive to become more than a gunslinging nobody. The West would be torn by disputes between various factions, and the player would have the opportunity to choose who to align themselves with, before ascending through the ranks and taking control of what is rightfully theirs.
The folks behind The Witcher are going full dystopian with the highly-anticipated Cyberpunk 2077, but what if they were to blend the landscapes of The Witcher 3 with the FPS mechanics of Cyberpunk 2077? If you ask me, that alone has the makings of a phenomenal game.
However, what CD Projekt RED brings to the table is a lot more than that. The studio's world-building is second to none, as there is nothing in the environment of the world that isn't dynamic and important. Rockstar's latest trumps most other games in terms of realism and smoothness of play, but it doesn't feel quite as full of life as The Witcher 3, nor quite as promising to explore.
Maybe an outlier on this list, but hear me out. FromSoftware has decided to drop build variety in favor of a particular class for Sekiro, so who's to say that they couldn't push the gun mechanics from Bloodborne in a direction of their own? Unlikely, but it's worth speculating on for the sheer potential imbued in the hypothetical possibility that they would consider working on a gun-toting Western.
Imagine having to fight a Souls boss, but instead of having to fight with a sword and shield in a castle, you're fighting with a revolver in a tavern. This wouldn't be a spaghetti Western, nor would it be any other kind of known Western for that matter, as it would likely be composed of a fragmentary narrative told through cryptic language. Also, there would probably be at least some aspect of being undead involved. That sounds great to me, though. In fact, this could be the best idea of the lot.
BioWare bring characters to the table. Every set of companions in a BioWare game is constituted by a group of absolute misfits who are all utterly unique and brilliant in their own weird ways. From the Drell assassin Thane Krios to the Qunari bruiser that is Iron Bull, BioWare always assimilate a cast of some of the best characters around. If this were to be applied to a Western, you could bet that there would be all kinds of unique and energetic personalities to bounce off, as your protagonist would lead a band of the best and the baddest that the West has to offer. If you want a Western filled with the most intriguing characters you can think of, then you'd better write the old BioWare team an email on why they should gather the troops to start a new Western game studio called WioBare. A space Western would be very cool.
Probably the studio I'd like to see try this most, although the second least likely to do so after FromSoftware. Naughty Dog make games like no other studio in that their dialogue is simply paralleled. Neil Druckmann's team can't be touched on that front, as every single line of The Last of Us and Uncharted feels like it had to fight for its place to be included in the full game.
Naughty Dog games are funny, dark, warm, and deeply complex. Their shooting mechanics are also pretty intuitive and fun, too, so they've already got the infrastructure for a Western game. Also, it would be pretty cool to see how their environmental design puzzles could be implemented into a Western setting, be it crossing a river using a makeshift raft, or using some classic Crash Bandicoot TNT to blow a hole in the wall. Actually, a Crash Bandicoot Western could be great—spin to win!