If they would simply change their policy so that every reasonable suspicion of abuse must be reported to the police the 'two-witness' rule would become less of a problem.
The real issue is the unspoken law that no JW must ever 'bring reproach on Jehovah's name'. The elders will not take responsibility to report abuse and the victim and JW parents are under pressure not to do so.
JWs don't report other JWs to the police. Muslim communities don't go to the police. Orthodox Jewish communities don't go to the police against other Jews. I would guess that the Amish are similar. This is what allows abuse to prosper.
If they changed the 'two witness rule' but didn't change the policy on reporting abuse to the authorities nothing would improve for victims. Abusers would still be protected to carry on abusing. Even if they are DFd they are free to carry on abusing new victims in the wider community.
The irony is that the unwritten policy of not washing dirty linen in public has resulted in more reproach than they could ever have imagined possible. And yet they they refuse to make any changes. It is this irrational position that makes me wonder who they are protecting.