Very interesting question, BW.
Let me make a try:
We know attitudes are formed from belief; hence belief about what happens after death would certain shape one’s attitude. Hence death may be part of a design (not the result of sin). In limited view, speed breakers on the road are inconvenience or annoyance, but in big picture, they are good because speed breaker near to places like school prevents accidents that can happen to little ones who may come on to the road carelessly.
Similarly, in limited view death may appear as a curse, but in big picture, death would appear as good. ‘What if there is no death, if one goes on growing more and more vibrant physically, perfecting his skills and talents, and even growing in money power, influence ….etc.? He would probably behave like King David described in the Bible. He was a very humble shepherd boy to start with, then climbed heights, finally became king of Israel, and he seemed almost invincible… then he began to add more wives and numerous women to his harem, he went to the extent of treacherously killing his faithful friend to steal his wife. If people grew extraordinarily great in certain aspects/skills, many of them become callous and arrogant, and it makes life a hell—for them and for others.
But when the body is in reverse growth towards complete collapse [death], people in general begin to lose the basis for keeping their desires and self-importance. Thus death serves a purpose!