Re: The shoulder grab - where does this come from
I can't speak to the Koryu element, I'm on the look out now though. Are you differentiating between Kata and Sode also? If you include both Kata and Sode, there are around 15 techniques done by Ueshiba in Budo Renshu that come from this attack. It's a surprisingly large number of techniques from this type of attack compared to other attacks show in the book. So Ueshiba had an interest in this sort of attack, and a pretty big one. Most all of them include Uke striking down just after he grabs though, and this is something we don't see in a lot of in modern Aikido practice.
I've never really officially studied Judo. But I've done Judo randori, and done jacket and sub wrestling with lot's of Judo guys quite a bit. The common Judo grips is a Mune (or Mae Eri Dori) with the right hand, and a elbow level Sode dori grip with the left. Although that's just a fundamental position, lot's of that happens while moving around trying to throw. As you get better at grabbing your hand gets trapped and crushed less often. There are also a few clever techniques that allow you to grab the gi really good and keep your fingers fairly safe. Although twisted fingers can always happen.
Speaking from my own personal practice. I used to dislike Kata dori, and didn't teach it too often. Then I realized that when we play our randori game, and people were trying to clinch with me, Kata dori was a common starting grip. That is to say, when we were moving around, lot's of times a Kata or sode grip would be the first thing Uke would grab, and then pull themselves in from there. I started training kata more, and found that lot's of the techniques helped.
I think the Judo connection isn't a bad one. It has been shown that at least for a short time Ueshiba was interested in making a kind of "anti-Judo". It could be that Ueshiba found it useful in quick multiple attacker situations, which is something I have personally experienced. Or it could have been something he just thought was cool, without any connection to anything else. One thing is for sure though, he really did like the attack.