Basically make it as easy as Mario Kart Wii, so fast random and lobby connections.
I'm absolutely very happy with the Wii Speak only for friends option. I stopped using my 360 headphone because of all the idiots on the other side of the connection.
The option to add anyone in a lobby to your Conduit FC list right away would be very nice (iirc that's also in MK).
But basically no lag + easy connection is everything I really want, the rest is bonus.