First off, I'd like to say... Amazing thread. You put a lot of effort in this, and it payed off.
OT: After reading the entire thread and pondering about the topic, i almost wholeheartedly agree.. Almost.
Infact my only disagreement is that The Uzimaki Cannot use ninjutsu. I understand that no Uzimaki Without Rinnegan Has used Ninjutsu, But i dont think that they are unable to do so. My reason being is that, Like you have stated, The Uzimaki are most known for using which techniques? Sealing Jutsu.
I feel That, In order to emphasize this point, Kishimoto(possibly to tie in The sage's Lineage) Focused only on sealing jutsu.
My only other argument in this matter would be, The final requirement to become a Genin, and graduate the Ninja Academy: Bushin No Jutsu. Kushina would've had to have done this to have become a genin and so forth, Thus; The Uzimaki may very well be capable of ninjutsu. (Though it does make one wonder how Rock Lee made Genin..)