You can still set a departure time and check the precondition box. If the car is connected to an EVSE, it will do both, but if not, it will just precondition the cabin. It's quite inexpensive to pick up a tablet (it doesn't have to be fancy or with a large screen) and just use it to setup preconditioning. As long as you have access to the internet (Wi-Fi, cellular is more expensive and an on-going charge), a cheap tablet with the free app will give you access for that. BMW has not allowed a browser webpage to do this. I'm guessing, they feel the app is more secure.
As far as I know, the departure time and preconditioning feature is standard on all i3's sold, at least in the USA.