For reference:
lichess.org/featuresI especially love all the features introduced last year around puzzles and blogging.
And I also agree with the idea of "not just copy that other website". Indeed, every time I read "lichess should do X" and X sounds to me like "stop being lichess", I feel a friendly reminder is necessary that lichess is open source and not only you can request features but also forks can and have been made to create other variants and games servers based on this powerful base. Not to mention other beautiful projects that are also open source and not based on but "friendly" to lichess, as the mentioned pychess.
Just saying maybe bughouse or 4player chess find their way somewhere, not here. As a chess player, my interest in them is not enough to start such a project, but as a software developer you may likely count with my contributions if someone does.