Here's an interesting article on this topic
here on Aikiweb.
The late Ken Cottier, one of the Western pioneers at Aikikai Hombu Dojo in the 1960s, used to say that iriminage was the one technique that Ueshiba O-Sensei created himself.
But then, the modern form of iriminage was argued by Stan Pranin to be a creation of Kisshomaru Nidai Doshu.
The Daito Ryu club I visit definitely does iriminage. And a very effective one at that (and it's not one of those ‘aikijutsu' places that do aikido with punches).
Then again the lines blur as in the beginning Ueshiba taught Daito Ryu. So even if he did come up with that technique, it could still be in DR now
So interesting question: did Takeda do iriminage? Maybe the Soden books would shine some light on that.
Btw one thing to keep in mind is that most lines of DR itself have, I believe, gone through quite substantial changes, probably as a result of work done by Sokaku Takeda's son. It was interesting to find that Amatsu-Sensei and presumably his teacher Hisa-Sensei (Menkyo Kaiden) use aikido type names for techniques which are not unrecognisable from their aikido counterparts (ikkajo, nikajo etc are different from their meaning in other branches and basically the same as in aikido). I would not be surprised to find that the Soden books use ikkajo, nikajo etc.