False accusations for any crime should be punished with the same sentence that would be given to the accused if he was guilty. If you falsely acuse someone of rape, you should get the same jail time that is given to rapists.
What happens if someone rapes me, and I accuse him, but then cannot provide enough evidence? Do I end up in prison?
There would still be the “beyond reasonable doubt” standard applied to false accusations - just like every other crime.
Rapes should be reported to police, as soon as possible, not to Twitter 10 years later. If it cannot be proven that either party is right, no one is sentenced.