I must tell you again, great thread. And to add, in regards to Sasuke and perhaps one of the reasons why we haven't seen his Final Susano'o in well over a year is that perhaps it is currently undergoing these changes, losing some of it's Karasu-Tengu like form over his past few battles.
If seeking and gaining knowledge, rather than remaining in ignorance, can metamorphose one into a Daitengu, according to Tengu myths, then, perhaps Kishi may go a similar route with Susano'o transformation this time, rather than growth through hatred as we've already seen. There have been many, many occasions where Sasuke has gained knowledge by explanation, or gone out to seek knowledge, rather than choosing to remain in ignorance, even in the most recent chapter. In his fight with Kabuto, he was given a run down of his team members abilities and clans, the Uchiha's past and their usage of Izanagi and Izanami, and Itachi showed him the events leading to and the Uchiha's final moments through his own eyes. Further when Sasuke seeks out the purpose of Shinobi and Villages, and obtains what he sought from the Hokage. There are many examples, too many for me to honestly locate and list each instance, enough for me to suggest that it is an obvious trend.
It would explain many things, like, why Kishi, though he typically takes no time in showing off new abilities, has chosen to hold off for the proper time for it's re-reveal.
