There are many GS BMW's that have done the IBR. Granted, they have drive shafts, but much like your motorcycle they don't have large fairings, and as the route changes each two years, sometimes they are helpful for the bonus locations which can be down dirt or gravel roads.
Usually the motorcycles in the IBR are ridden hard, and put away wet. Oil changes don't happen during this rally. Drive shafts reduce the maintenance time during the rally, as do drive belts. Can you get a drive belt conversion for your motorcycle? Just a thought.
If I might be direct with you, you've only put 15,000 miles on your motorcycle yourself. That's nothing compared to what the IBR riders do. These guys and gals will ride 1000 miles for a hamburger. They'll run across the country because they are bored. They are not like most people, and based on your mileage they are not like you. The IBR is very expensive ("11 days, 11,000 miles, $11,000" is the unofficial motto many of the riders use), and in spite of what they claim it is dangerous. This is an endurance race, where winning riders will forgo sleep for days, speed in triple digits, ride at night in forested areas with deer, and push their bodies and minds to the point of exhaustion and fatigue and in some cases hallucinations. Can your motorcycle do it? Yes. Can you do it? You got to answer that. There are many other rallies that are only a few days and a few thousand miles. How many of those have you completed? They are a blast, and you'll get to learn a lot about yourself and your motorcycle without incurring the expense of the IBR. Many IBR riders also enter these rallies, so you'd get the meet the IBRers and learn from them. Most are very welcoming to sincere interested people, and I can't recommend this enough to you.
Also, have you read Against The Wind, a book about a finisher in an IBR. It appears pretty objective, and is a fun read.
Oh, are you in the IBA? I think that is a requirement to enter the IBR.