Best discussed with a competent 33/34 act lawyer .... but my layman's understanding is that in general securities cannot be offered to the public unless they comply with the 33/34 act, which is essentially an agreement to provide current and sufficient disclosure.
Under exceptions, such Rule 144 or Reg D, you can avoid this onerous process. However these securities are restricted from the general public. If you borrow restricted stock and short it in the market, regulators will say you are wilfully circumventing the 33/34 Act.
There might also be a deemed underwriting problem - ie you are in fact acting as a underwriter even though you are not registered to do so, this is Reg M.
I've only described the problems of course, I can't speak to the solutions. I'm sure there are many creative ideas on how these problems can be solved.