My understanding (based on 2011 purchase) is that each dealer is allotted a certain number of production slots covering the model year. Presumably, this is based on sales history. Each slot has a planned build date. Many of the slots specify predefined models and options. These vehicles are delivered to the dealer during the year and are those you find on the lot, ready for immediate sale. Other slots are "open", i.e., the specific model and options are defined by the dealer prior to the scheduled production date to fill a customer's specific order. The dealer is allocated some number of these open slots and will use the next one available to fill your order if the desired vehicle is not available or if you want the PCD option (see below). Sometimes a nearby dealer may have what you want and your dealer will work some sort of trade to obtain it for you. If the dealer uses an open slot, they should be able to tell you the scheduled production date and, based on this, an approximate delivery date.
So, I don't think that there is any way to bypass the dealer in the ordering process. Maybe some day... At least buying through a dealer begins a (hopefully good) relationship since you will undoubtedly make use of them for maintenance while under warranty.
Highly recommended: If you can get to the assembly plant in Spartanburg, SC to utilize the Performance Center Delivery option, do it! You'll still pay the shipping fee but, for that, they put you up at a hotel with dinner the night before, transport you to the Performance Center the next day, treat you to some on-track time in their vehicles, provide personalized delivery of your vehicle, treat you to lunch, and provide a tour of the assembly plant. Our delivery person spent more than an hour with us, introducing all the features, making certain our key fobs were correctly synched, etc. Since this was our first BMW, it was extremely helpful. She also provided a contact number which I later used to ask for clarification on one of the controls. All of this is really interesting and great fun. Most everyone learns something new in the process and the staff is infinitely patient. The vehicle was for my wife, replacing her 1991 Ford Explorer with some 225,000 miles on the clock. Talk about a leap forward! And they treated her like a queen throughout the process. The one disadvantage of a PCD is that it may add some delay to the process since they have to schedule you for the delivery and it's a popular option.
Dave @7500 feet on the plains in Colorado
2011 X3 35i - Blue Water Metallic