[B]Non Roof Bike Rack Options[/B]
I used to have an InvisiHitch (now re-named ExecuHitch) on my previous car (X5 that my wife now drives), and I looked into availability of them for the W205 seeing as I know you can get them on the current 3-series. They didn't have it available yet at that time, and it seems like they still don't. That meant I couldn't continue to use my hitch-mount rack.
Your only real option other than a roof rack is a trunk mounted rack. Go with one if you must, but they are not as secure as a roof rack and will eventually damage your paint no matter what you try to do to avoid it. Either the rack itself with rub on the paint or somehow the bike and/or wheel will hit the bumper causing damage. They also restrict your access to your trunk while using the rack, something that was a non-starter for me.
With a roof rack (or at least the one I have), once you go through the initial installation by setting up all the bars and towers, it really doesn't take that long to take the rack/bars/towers on and off the car. To put the entire rack on my car, it might take me 5-10 minutes, and that's mainly because i'm extremely meticulous about it.
I've also never had an issue with height restrictions while my bike is on top of the car. The top of my seat (highest point) is lower than the roof of any UPS/FedEx truck, so as long as those can fit on whatever road you are driving, you will be fine. Also, the roof is low enough that you aren't lifting the bike all that high up in the air to load/unload it.
And also too, the look on someone's face when a car with a bike rack on top pulls away from them is priceless.



