speaking of bugs, Franz Ferdinand could have ascended the Throne in 1910. Franz Josef had a very severe case of pneumonia, and nobody, even his doctors, expected him to survive. He was given the Last Rites, and as he lingered some initial plans were laid for his funeral. FF was ready to leave the Belvedere at a moment's notice and take up residence at the Hofburg. So, make the illness just a tad more severe, and voila; serious enough reason to butterfly away the trip to Sarajevo.
As has been posted here before, by 1910 - 1914, FF had given up on the so called "trialism" and wanted to find some way to make Dualism work.