"Un-converting" a Fixed Gear

With the impending move to a more interesting terrain, I'm contemplating adding a rear deraileur to my rain fixie. Also, we found out that the import duty for my car alone, will run in excess of $10,000 US- so it looks like we are selling both cars before we move. Obviously, this will also save moving expenses. Without a car, I'm also thinking of tossing a rack on the old black bike, and turning it into a frankenbike commuter. I'll probably keep the 42 chain ring and avoid a front deraileur, and toss a thread-on 7-speed in the rear. I'm guessing bar end shifters would work the best, since this frame has no down tube braze-ons. Of course it will have lights for the eternal darkness that is known as winter. Overall, it should be a very ugly bike by the time I'm finished!