Which begs the question as to why Akatosh would give birth to Alduin in the first place. It would seem that Akatosh contradicts himself because he is the cause of the world's ending and it's salvation. Being that Akatosh is the god of time, it's easy to suppose he knew from the beginning that Alduin would devour the world. So why create the Dragonborn to begin with, if Akatosh created Alduin with the full knowledge that he would destroy the world?
Point one, incorrect usage of "begs the question". Begging the question is a logical fallacy, a form of circular reasoning in which an assumption is used as evidence in it's own support. It does not mean "begs that the question be asked". Sorry, pet peeve of mine.
Second, you have to understand the nature of Mundus and reality in TES. In the beginning, everything was one big glob of energy we call "the Godhead". The Godhead split into two globs, positive energy and negative, creative and destructive, order and chaos, which we called Anu and Padomay. The interaction between these two forces began to create swirls of mixed energy called "Et'Ada" the first of which were Akatosh and Lorkhan, but there were many others. When Lorkhan convinced the other Et'Ada to create Mundus, the nine that remained trapped there had to divide and recombine their energies into new forms in order to survive, a process with divided them into all the races of Nirn, including dragons.
Alduin "eating" the world is just a mechanism by which that energy, which was once one big "glob", can reform. Alduin and the Dragonborn are not so much "decisions" made by Akatosh so much as they are a physical representation of the Godhead attempting to stitch itself together.