It's certainly interesting, but I dislike how Kubo explained Masaki's death. It seems a bit lame and farfetched.
As for Uryuu, there are two possibilities in my mind:
1. Double agent. Sent (by Ryuuken?) to infiltrate and sabotage the Sternritter. This is also an excellent way for Uryuu to become stronger.
2. My favourite crazy theory: Uryuu has been a member of the Vandenreich since day one, and has played an intentionally weak and passive role to observe Ichigo & friends.
Revenge (think about Mayuri's past actions toward the Quincy) is definitely in the realm of possibility, but it would also clash with Uryuu's overall character and his strong Quincy pride.
