I think this has more potential than the OP considered, but you have to optimize for asynchronous communication. Have conversations in chat, but if there's someone you want to talk to in particular direct message or email them. If the two of you seem mutually interested in each other's ideas, set up a time to have a live conversation
I feel some sympathy for grad students, but am personally quite excited to see how this plays out since I've wanted virtual conferences to be more of a thing since I started pirating Blackhat/DEF CON videos as a teenager :)
Or you split the difference of about 9 hours of time zones to accommodate the western US through central Europe with the event starting about 7am in California and ending around 9pm in Europe. And, for a US event, you basically ignore Asia.