I often wonder how much an influence Nishio Sensei had over the post war uchideshi. The 'seiki ryu kenjutsu' I learned as part of Kurita Minouru's school was HEAVILY influenced by Nishio Sensei's aiki-toho and the aiki-ken coming out of Iwama. I got the impression that Nishio Sensei was known to the uchideshi as a sort of 'go to' guy for weapons work. The way it was presented to me was that Kurita Sensei would "sneak out" to see Nishio Sensei whenever the opportunity presented itself. I don't know why this was the dynamic, possibly because it was time away from OSensei?
a) I am sure that Nishio Sensei was someone who influenced the younger deshi. Certainly, he was someone who brought outside training into his Aikido while at the Hombu Dojo. As an example for the younger deshi at Hombu, especially at a time when some were choosing not do do much weapons training he stood out. I have never heard Saotome Sensei say that he was directly inspired by Nishio Sensei but I always felt that their two approaches (not the actual technical work) were the most similar of any teachers I've encountered. Mary Heiny told me that it was always Nishio Sensei and Saotome Sensei who would do the tachi dori and tanto dori with live blades at the all Japan demos. I see a lot of Nishio's spirit, if not actual technique, in Saotome Sensei.
b) Nishio's training seems to have been largely well documented. It's hard to say exactly because he saw himself as a creator, someone whose job it was to go beyond what he had been taught. He credited Yamaguchi Sensei and Saito Sensei with equal but quite different influence on his sword work but it is clear that he didn't imitate either one but rather took inspiration to develop his own work. Of course he took his iai work out to the point at which it is a recognized iai style now...
I think it is safe to say that Nishio's work was well developed as a system that could be reproduced, like Saito Sensei's, but was also
the most eclectic in it's influences and, I think, unique to him. No one else looked like Nishio Sensei. I also think that because his work was so integrated into his overall system of Aikido, it makes it difficult to simply take this or that out of context into ones own system. You really need to train with someone doing well versed in his system to get much out of his weapons work.
He was a giant in my opinion...