1. Rear Brake.

2. Cable routing for rear derailleur and rear brake, going to be more of a hassle than you might think at this point.

3. In this forum there is a thread called commuter bike pics, about 10 minutes perusing that may change your mind about rack mounts. College students on inexpensive bikes carry back packs. More mature commuters are more likely to be able to afford carbon frame folders and they are more prone to panniers and racks. However I could see the addition of a large frame bag as being one possible compromise.

Good luck with your endeavors.