I don't think that Headlocks and body locks are outside of the scope of what Aikido could be, I just think they are out side of the scope of it's traditional syllabus. I've never seen footage of, or heard a story of O-sensei teaching headlock or body lock escapes. I don't see them listed on the hombu list of techniques for testing.
However a close relative that we have in our system is ushiro kubishimi. Interesting thing about Kubishimi is that it's a choke with a wrist grab. Why do you think that wrist grab is in there...
yes we do have ushiro kubishimi in our formal system as well.