Doesn't BG3 already kind of have the mechanics to implement your #3? Currently, any player can try to rest for the night, but the other players have to accept? (This is true in my 2-player game. I assume it's the same in a 3-4 player game)
Seems like Larian could easily just extend ^ and allow anyone to suggest waiting for night, but the whole party has to agree via pop-up. Again, D&D is collaborative and you have to assume that the players will cooperate to some degree.
To solve your "what about moment-to-moment gameplay where one player can enter a turn-based battle in an area while others are roaming freely?" objection:
-You could also have time pass according to the host's clock. If the host is in combat, the clock is frozen for everyone (like how the game currently works all the time). If the host isn't in combat, time passes.
To make it further easier for Larian, I'd be fine with it not changing from day to night until you change loading zones. If the "clock" reaches 6pm while you are exploring, it stays lit out. However, when you enter a building/go to camp/fast travel, the time would then update.
