I have known a kid who has been coerced by her mother to report abuse by her father. Though the father was not fellowshiped, he did loose his privileges on the grounds that he could not preside over his own family. In the meantime, an anonymous call was made to child services and they asked that the father move out of his own house until they figure it out. In time, Child services found that there were holes in the kid's story and let the father move back in.
Later, once an adult, the kid finally admitted that she had been coerced and that she made up the stories.
The reality is that false testimonies do happen. Still, the two witness rule is not flexible enough. For the very least, abuse claims should be reported to the police. Then, under agreement from the victim, the law and the elders should work hand in hand and handle cases properly. The two witness rule could still be applied for disfellowshiping, however, unless the perpetrator is cleared by the police, he should loose all his privileges and never allowed to be alone with kids.