think about it, how much fun would it be to strategize in Honkai Star Rail with your friends, clearing herta's simulated world with them or an entirely new mode for example a boss rush with different floors. this is what we are currently missing from this game a way to play and connect with our friends, it doesnt need to be anything complicated, the way it can work can be similiar to genshin when someone joins your world/lobby they will be able to use some of their characters depending on how many players joined. we are aware that the game is mostly story driven, thats why this is just gonna be apart from the main story and only focus on different modes that can be implemented in the future or use the ones already available ( as already mentioned before hertas simulated world can be an example) last but not least  importantly adding a chat during the fights could also be useful in order to communicate your strategy with your friends.