Build a teleconferencing app tailored for parties rather than meetings. The needs of parties are very different than meetings. I'd suggest there be a central channel where everyone can participate and talk, with the video on that channel being something that sets the theme of the party (a bonfire, a movie, a performance). Then it should be extremely easy to click on participants and engage one or a few in conversation. Perhaps those side video conversations could bleed into the main channel (maybe audio only) so that people in the main channel can overhear and potentially decide to join in. Think about how people interact at parties and try to tailor video conferencing to work better for social gatherings. Security should be built in to reduce worries about privacy so people feel free to talk; no routing of everything through a central server, peer to peer only; recording should be only by consent (though there would be no way to stop analog recordings). There are a variety of video streaming libraries that might make building such an app easy. It should be trivially easy to understand and use. I think it might almost be possible to use existing teleconferencing apps if everyone could join two channels, the main channel and a side channel, using two devices, e.g., a laptop for the main channel shared by several people, and individual phones for the side channel for smaller conversations. Coordinating all that and explaining to people how it works might be difficult though, so putting it all into one app with an intuitive UI would be useful. There may be issues such as how to deal with audio feedback noise and easily joining and leaving side conversations though. You don't want people to have to send invites and accept them to set up a side conversation, you want it to be instant and easy.
Even if the coronavirus ended tomorrow, I think this would be a popular and widely used application.