To the contrary of common belief, the Imperial Cult of Shireroth doesn't automatically gives the Kaiser the position of God. Even after the death of the Kaiser, there is a big chance that he will be nothing more then a deity or spirit who has the task to protect the Imperial Republic in harsh times. The Cult is not a religion on its own, but an extension for religions: the Kaiser has a position of demigod and should be worshipped or at least be respected as messenger or representative of the Gods.
The Imperial Cult was established during the reign of Kaiser Gaelen IV in an attempt to revive the practice of religion(s).
So, the cult is not one of personality but one of national identity. Not the person is a deity, but the Kaisership gives the person those powers. Once dead, the former Kaiser loses his position as demigod. The Gods then decide what to do with the spirit.
During his life, the Kaiser acts as not only the ruler of the Empire, but also has a religious position: he is the protector of his people, by the grace of the Gods themselves. As result of this, he's granted the Swords made by the Gods, which can only be used by a deity or God. For this, only the Kaiser can use the sword(s) on Micras.
The Kaiser: Bringer of Stability
The Prophet Lor'Hux proclaimed long, long ago:
"Shireroth is an enormous Realm. Established during the rule of the mighty Raynor the First and with the help of the Gods. With the Sword of Fire, made by Mors, the Demons were defeated and Raynor ruled his Empire with an iron but fair fist. Soon became evident that Raynor, just like his descendants, enjoyed a deity status and it became clear that the Fate of the Empire was connected to the Fate of its Kaisers. As the Gods had granted Raynor and His descendants the power of establishing and developing a huge and diverse realm, they also became the symbol of Stability. Without a Kaiser the Empire will decline and ultimately collapse. For the sake of protecting the Empire and its citizens, a Kaiser is needed who will rule the people. The Kaiser should be thanked for keeping the peace by worship in the temples and by showing respect to Him in the streets. That's the wish of the Almighty Gods!"
Kaisers who became Gods
Several Kaiser have been given the honour by the Gods to become a God or demigod after their death. In Cedrism e.g. the God Mog is probably most famous: Kaiser Mog I died and the Gods, impressed by the political blunder he had made, made him the Moogle-God of Political Blunders.
In recent times no Kaiser have had the honour of becoming a God, nor a deity.