According to the Constitution "no person holding an Office of Trust or Profit under the United States, shall be appointed an Elector. " Bill Clinton is an elector from NY and he receives both a pension and office expenses from the US and hence receives a profit for his office. So he seems to be an illegal vote for Clinton.
So by your logic, any former employee of the federal government who receives a pension is barred from being an elector?
I interpret "holding an office" to mean currently in office, and thus excluding benefits given to former officeholders. And office in this context clearly doesn't mean a workspace, but rather an official government elected position.