I felt like we ALL got too attached to Arthur, and I can see it might just be like Red Dead Redemption 1 where you play as Jack.. but let’s have it different by allowing you to play as Arthur again, for whatever reason you could come up with.. 

Perhaps as a option like him being sick from tuberculosis was all a dream/nightmare and the game could give you an option to choose which path you wanna go through, maybe have an option by the end of the game to continue as Arthur or play as John, or the option to switch characters in a way.

Just some ideas but if you could then it'll be a really great thing from you Rockstar Games.