An invite option would be cool indeed, much needed.
I have had another issue that this could help a bit. It seems that when I create a private lobby and race with my friends then if I get dropped from the lobby server I can not go back in. The lobby does not show up under my friends lobbies nor in the main lobby screen even though one of my friends is now hosting the lobby.
The result if that I have to create a new lobby if I get dropped from a lobby I created and that is rather annoying.