I've came up with so many ideas for this, but they all make me sound insane. Rightfully so as well.

I believe the victims should be able to choose anything they want for however long they want. If they choose a punishment but are to afraid to do it on their own, I believe there should be help.

The device I came up with in my head and have thought about so many times now is something that would work on either sex. A large 6 foot tall pyramid shape that can open down the middle sort of like a giant reverse bear trap. Made out of conductive metal, it should be slowly inserted into the body until it is all the way through, superheated the whole way to cauterize anything inside, and slammed open; effectively splitting the person from the inside until their death. People should be on site to try and keep them alive as long as possible.

Because that is what it feel like to be taken. Slow, so that it eats away at the brain and sanity until their demise which they will plead for. Like every victim. It tears apart mind and body and covers up the wounds just long enough to keep them suffering for as long as possible. An accurate depiction of what they've done, plus death. Which is a route many victims also take, sadly.