I see only benefits to releasing something like this proposal. Even if absolutely nothing comes of it, we all learned some interesting Physics, Musk learned what happens when you publish your unfinished proposals, others may start thinking about the problem and come up with a different solution and finally, the cynics can point out how bad the idea was to begin with. Of course the cynics won't realize that working on these ideas and in this case even publishing the work are the reason that Elon Musk runs Tesla and SpaceX and they don't.