Is the person designated by the deceased to lead the funeral prayer to be given precedence over the mosque's imam?

The imam of the mosque has a greater right to lead the funeral prayer for the deceased, even if the deceased bequeathed that someone else lead it, because this falls within the imam's authority. This is based on the Prophet's (peace be upon him) saying: "A man should not lead another man in prayer in the latter's place of authority." However, if the imam waives his right and allows the person designated by the deceased to lead the prayer, then there is no harm in that. If neither the ruler nor the judge is present, then the imam of the neighborhood has the greater right to lead the prayer.