People have done what you are thinking of - I once had a 22' travel trailer that had been modified with a swing out rear door and I carried a Mini-Cooper race car in it. Be aware that the tendency will be to build your "house" stuff at the front of the trailer, and your "toy" section at the back, and that with such a small trailer there will be a very real tendency to over-load the back. For example, a load of fire-wood - a cord of seasoned oak can weigh close to 3 tons. Get much of that behind the axles and nothing much up front, and you'll have an issue...
Brian