"Aikido" tends to be defined with a very broad brush, as you seem to be doing here, and I have long believed that to be dangerously misleading.
Here's an interesting thing. My own aikido teacher was originally a student of Gozo Shioda, even though he has been in the Aikikai for decades now. I've been increasingly aware for quite a while that there are mismatches between the way his aikido works and how most Aikikai shihan teach techniques. The mechanics of his body movement seemed more subtle and more softly persuasive than what I had seen in what you might call the "Kisshomaru school", and in a way that is nothing to do with mere relaxation or softness in themselves.
After having noticed a certain person's name and opinions appearing regularly on this forum a few years back, out of curiosity I registered for a workshop he was due to give here in the UK. At that workshop, I had an epiphany: all of a sudden, I saw that my aikido teacher's "aiki engine" was almost identical to the method this person was showing (even though the outward forms they show are very different) and, what's more, he was showing us a set of exercises he learned from his Daito Ryu teacher that were clearly designed to develop these skills. I could see that both men's movements were fundamentally based on spirals and opposing forces, which I have never seen in the modern Aikikai Hombu Dojo style. Watching footage of Shioda Sensei and some of the senior Yoshinkan shihan, I can now see very similar mechanics to what I have seen of Sagawa and Horikawa from Daito Ryu.
Incidentally, I've come to the conclusion that the "aiki engine" of Koichi Tohei and his students (I assume this also applies to Maruyama Sensei, though it's been ten years since I saw him last) is different on a profound level from those of either modern Aikikai aikido or of the Daito Ryu / Shioda lineage. It seems very much based on the combination of deep relaxation with a very efficient use of gravity.
Now how this relates to Morihei Ueshiba (who of course had a Daito Ryu teaching diploma from Sokaku Takeda) is a whole other question...
Well, these conversations never really go anywhere, so I'll just note that, while I agree that Shioda shared body methodology with some daito ryu people, there are major differences too, which are even more pronounced in his students.The more that I've trained in DR, the more profound I've found these differences to be, which is one reason why I advocate people actually train in the art in a prolonged manner. Shioda met and trained with Horikawa BTW. I also think that the 'engine' analogy is not really an accurate one, for reasons too lengthy to go into, but to use another analogy, taking the same 'vitamins' from a food or from a pill isn't really the same 'thing' either.