Pre war there was*:
▪ Zenzaburo Akazawa (born 1920) since 1933
▪ Masahiro Hashimoto (born 1910) since 1931
▪ Takuma Hisa (1895--1980) since 1934
▪ Noriaki Inoue (1902--1994) since c.1921, nephew of Morihei Ueshiba
▪ Ikkusai Iwata (born 1909) since 1930, 9th dan Aikikai
▪ Hisao Kamada (1911--1986) since 1929
▪ Minoru Mochizuki (1907--2003) since 1930, 10th dan (received from the International Martial Arts Federation)
▪ Aritoshi Murashige (1895--1964) since 1931
▪ Gozo Shioda (1915--1994) since 1932, founder of the Yoshinkan Aikido
▪ Rinjiro Shirata (1912--1993) since 1933, 9th dan
▪ Isamu Takeshita (1869--1949) since c.1925
▪ Kenji Tomiki (1900--1979) since 1926, was the first 8th dan awarded in aikido in 1942.
▪ Shigemi Yonekawa (1910--2005) since 1933
▪ Tsutomu Yukawa (1911--1942) since 1931
Ellis mentioned Takuma Hisa, Chris Moses likes to mention Noriaki Inoue, nobody has mentioned Ikkusai Iwata (We don't seem to hear much about him even though he was active in the Aikikai up until a ripe old age . . . any body know why? Peter, thoughts?), Minoru Michizuki has been mentioned as has Gozo Shioda, Rinjiro Shirata hasn't been talked about, Kenji Tomiki has been listed, I didn't list the others because I don't think they were significantly active after the war. (Please correct me if I'm wrong.)
All of these individuals were students of O-sensei prior to, or at, the time that Budo Renshu recorded a sampling of techniques being studied and I would be very surprised if all of the students listed above weren't familiar with its contents (It was a broad sampling but by no means comprehensive), I know one did.
Another very valuable historical and marker for O-sensei's pre-war waza are the Noma dojo pictures. This is, reportedly, a huge collection of photographs many of which haven't been published. This collection poses several problems however. 1. There is limited access. (I only know of one individual, outside the Ueshiba family, that has access to them all. But things can change, and, I could be wrong here.) 2. The photos are in disorganized jumble. 3. It will take a a person with knowledge of (that period's) Daito Ryu, and (that period's) Ueshiba's practice to best be able to "connect the dots." (Given the present topic of conversation, I think we can see the problem finding living individuals that satisfy those criteria.) 4. Given all of the above, it will still take a significant amount of time to accomplish the task.
*According to a list found on this page: http://en.wikipedia.org/wiki/Morihei_Ueshiba
Yeah, I'm lazy!