Oh it is definitely not something I'd ever expect to actually happen, but at the same time, I'm just wondering about whether or not it can be done. The Constitution doesn't say anything about the nominee's willingness, so if the president says they are nominated and the Senate votes to confirm, I would think they would assume the duties of the office they were nominated for regardless of whether they wanted it or not.
In fact, if it does indeed work that way, I would think POTUS could effectively force a person to assume the responsibilities of some office by constantly renominating and getting the Senate to confirm each time the person in question quits