That's interesting. I think right now its a longshot. I think that the MCU version of the Western characters are probably going to be modernized as "actors in a long running Cowboy/Western TV show" and that the modern version of Kid Colt could be the grandson of the 40's film version of Kid Colt that was funded by Howard Stark. By making them modern day, they can have easier access to modern weapons and technology than they would if they were time travelers. Could also modernize their backstories, such as some of the cast might have been child actors and studied formal acting in places like Los Angeles, New York and London. Others could be US Military vets who see acting as a way to deal with any trauma that might have happened in the military. It would be those actors that have connections to modern weapons and technology.
Note that the Agent Carter version of Kid Colt was an actor portraying a historical figure, not the actual Kid Colt.
I'd say making the Marvel Western characters into modern actors and soldiers with modern weapons misses the point of their appeal and putting them alongside the modern Avengers makes them stand out less, making them into just some more guys with guns.
Their strength imo comes from them being actual regular 19th century Western characters with revolvers and horses who may occassionally run into supernatural or sci-fi stuff because they happen to be part of the Marvel world.
Another interesting way they could appear is if they do something like American Horror Story: basically a series where every season is its own miniseries with an overarching theme. In this case about historical settings in the MCU. This way the history of the MCU could be explored and it can still have ties to some modern characters. For example:
- A 19th century Western season could have a focus on Two Gun Kid, Kid Colt, Rawhide Kid, Red Wolf, etc. And then they could have an episode about the mysterious 'Phantom Rider' (Carter Slade) that could have ties to Ghost Rider, an episode where a stranger (Ajak the Eternal) shows up in town and the main characters help her with something she needs to do, etc.
- An Arthurian Britain season could have Sir Percival of Scandia and the Ebony Blade, Morgan Le Fay, the Celtic sorcerer who would later become known as "The Ancient One", set up a bunch of lore for Captain Britain and such.
- An ancient Egypt season could tie in to Kang/Rama-Tut or Apocalypse/En Sabah Nur, it could have relevance for gods relevant to modern MCU heroes like Bast (Black Panther) and Khonshu (Moon Knight), it could have an appearance by Gilgamesh, etc.
- You could do a WW2 season which could have appearances of Peggy Carter, Howling Commandos, Union Jack, Wolverine, all the golden age heroes like the OG Human Torch, Whizzer, Miss America, Blazing Skull, Destroyer, etc.
- You could do a season set in Wakanda during the time of Bashenga, the first Black Panther
- You could do a season in Ancient China with ties to the Mandarin
- You could do a season set during the Jogunn/Asgardian war in Norway