Governor Manchin covets this seat, so he will do whatever best positions him to get it. He could wait six days, declare the seat vacant and appoint himself. If the law does not allow that, he could appoint his mother, wife, cousin to the seat and then run in the special election. He will be hard to beat in a special election.
You hit the nail on the head. As a West Virginian, I believe Gov Manchin will appoint his wife, and then he, himself, will run in the election.
He started this process when he appointed his wife to the WV Board of Education.