You haven't actually shown any incoherence. What you've shown is that we can think of the lives of persons as a series of numerically distinct but psychologically continuous stages. But the word "I" may not refer to person-stages but to the whole person of which those stages are parts or tokens. What it means for "you to die" is for there to be no more person-stages psychologically continuous with your current person-stage. We can still use the same vocabulary, more or less. This goes for any object that changes over time. My Venus Fly Trap isn't numerically identical with the thing that was in my kitchen yesterday, but they're still the same plant.

The point being that the only thing in the picture that can be considered a unitary object is the mind-moment. Subsequent, related mind moments are not the same thing. They are similar, and they remember being the previous ones, but they aren´t the same person.

Why is this a "should" question?

Because creating a new mind is a positive action. We must be careful about the minds we actually create, because we are responsible for what that mind does, and how it feels. A mind which never exists is unremarkable. If we chose to create one, we should be sure it is the right thing to do.