I'm willing to bet it would be a lot more itme and money than you're willing to spend to do it right. You'd need to find a P5 with a good rear end, cut that off, reinforce it a good bit and set up the interior like you want. Then you'd have to figure out a way to custom fabricate some kind of covering for the front side of the trailer, and I would imagine doing something like that on a car/trailer like this is more easily said than done.
I also don't know if I would really trust a P5 transmission to pull something that heavy.
But if you decided it would be a worthwhile project, it would be a very badass little project.