Should a Jewish person cremate a Jewish spouse, if that is their desire?

Sometimes directives are not to be followed.  There are higher principles at work and these principles trump personal choice. For example, if someone says to another “Torture me,” the imperative carries no weight and any listener would disregard the statement no matter the relationship between the two.  Philosophically, the reason is clear: our bodies are not our personal property to do with as we please.  Rather, they are on loan from God, as it were, and must be treated with the utmost reverence.  The reverence we give to the person extends even after death.  Here, the operative principle is “kavod ha-met.”  In light of this principle, a number of practices are contrary to Jewish law.  For example, leaving a body unattended, or mutilating a corpse, or embalming the dead, or viewing the body are all violations of the principle of “kavod ha-met.”  And so is cremation, regardless of any exceptions in early Jewish history.  The Jewish ideal is to return the body to the earth from which the very first human being was created (Genesis 3:19), bringing life full circle.  With all this in mind, the surviving family members must ignore the instructions previously given by the decedent and not cremate the body.   What may complicate things is the fact that not all the surviving family members may be in agreement and the fact that even after knowing what Judaism demands, the family may choose to ignore it.  Also keep in mind that many rabbis will not officiate at a funeral when cremation will ensue.