I totally agree with that, it's just that what you are describing sounds like a process I already have been going through (changing from muscle to transmission and manipulation of extrinsic forces like grf and weight). MAN I was stiff 2 years ago! (have been all my life)
But yeah I saw the same thing you did about the biceps firing. I'll keep watching that video but I still have not convinced myself that the power I am primarily using comes from those muscles. (They may be firing here and there, yet still be inconsequential to my main forces and movement-- there is a lot of noise in my motor system, I need to do more misogi ;])
so you're seeing the same thing i'm seeing. If Ikeda were to do those things in a tshirt, I'm pretty sure you wouldn't see any of that. The same goes for the other skilled guys I mentioned. The thing is, you don't fix that by continuing to do them with muscle, thinking that it's going to get softer. It doesn't work that way, IMO. There are joint connections that have to be strengthened to be able to hold you together against forces so that those muscles don't kick in. The only way those things get conditioned is by NOT using the muscles. You start soft with very little force, just short of that point where the muscles kick in. It's pretty boring at first, I will not lie, but it really doesn't take a lot of time to get to a point that your body can start supporting you this way from standard directions and then you can start working these things in more active ways that aren't directionally specific. You really should find some people in your area to work with, there are quite a few in Ca these days.
I can probably get something for you early next week. It may not be instant though, I have to look for it , but i'm still a noob so that's ok. It's the connection that I have to find , depending on how hard the person wants to grab, but once I have it, the kuzushi part is fairly easy and doesn't require outward movement from me. Keep in mind that i'm talking about light force here. If someone were to grab me and push through me hard, I'd still have tons of muscles kick in and it would all go to crap. That just shows that being able to do a neat trick isn't the pot of gold at the end of the rainbow. It's more like the most basic of things. Thinking about these things, figuring them out for yourself helps, but putting in the work is the only thing that gets results.