It does not seem like it is possible to start a server without the -sv.

I wonder if it would be possible to start a stand alone server in the background, as in another instance of the engine minimized when the player starts a server from a instance that was started as a client. So you would always start the normal game as a client and as soon as the player clicks on start server it starts a standalone instance minimized in the background and connects to it from the already running client instance. But that might not work.