What is Juha Bach's motivation? For everything Juha Bach is doing in the current Bleach manga, what is his reason for doing so? 

Also according to the Bleach wiki his official name is "Yhwach" with no reference to Juha Bach though, so I also wonder about that. What is his canonical name?
He now holds Hueco Mundo. Should he gain control of Soul Society, there would be no power considered great enough (in his mind) to threaten the Quincy race again. This seems to be my assumption.

Although i'm sure there's some sort of connection that's yet to be revealed to us as well. I speculate this connection due to the fact that Masaki's family is dead and there was no explanation given, unless we are to assume they perished in the Quincy genocides.