The limitation of death would no longer affect him. If he was immortal, then he could personally do whatever needed to be done. Mortality represents the limitation of time. Being only one person, in only one place, for only a limited time, one can do only certain things that relate directly to certain minutes and days and a certain culture and a certain place or series of places. Jesus rejected immortality as the devil defined it.
Death is death.
And therefore time is limited. Accepting our limitations Things, people, and time are the Three Great Limitations. Jesus accepted them. In accepting them, he became suddenly and decisively human. There is no other way to play the game.