What is needed in such situation is a one general idea(lack of unbalancing) to give him a global direction for his future training and a simple physical solution that he can use immediately to unbalance attacker. That was my reasoning when I provided some advice.
I agree, and let me be clear, I meant to "second" your advice. My post meant to say that I thought the 2nd video didn't follow the posted advice as well as the first, not that I disagree with the advice itself.
OK well as far as OP question is concerned-- the thread (and other ikkyo threads) has already done as much good as is possible on the net, I suspect. Your advice sounds good and with Curran shihan's advice and others' posted, it seems the OP is pretty nicely addressed.
In other words, beyond this point, this is intended as interesting (? to me anyway) discussion that has come up, beyond the OP's initial introduction of the topic. Should this be a different thread? I'm sorry if posting this is a bad judgement call. It's just net discussion.
As to why I used the term "trick" above:
Physically, a force only has 3 parameters: location, direction, and magnitude. So as a simple example, a tegatana contact near the elbow in ikkyo is close to a single point of contact. So, that is the location. Direction and magnitude have one value each, at each moment of time. (one value each, not two)
So the question is how do you manage or control the force there, over the course of the technique. Keeping 2 directions of force in mind, as a guiding principle for what you are doing, is simply a mental method of control (a "trick"). In fact, there is only one net force produced at each point of contact, not two. What I mean is that whatever directions you keep in your mind are just tricks that change how you manage your body (and the hundreds of forces that your body is producing inside, in order to produce your net applied force). Let's face it, nage and uke's hips don't touch in ikkyo. So there is no real force there.
A person might argue that any real force at a point of contact is the sum of some number of real forces you produce. In fact I agree. But it isn't two, it's probably hundreds! Each muscle produces a force. Even passive tissues like bone, skin, or connective tissue (and the floor too) produce force when pressed or pulled. Abdominal air pressure can provide force in any direction that it gets pressed from.
So-- as much as you can argue that the force you produce is (for example) the sum of a hip-to-hip vector ("vector A") and a tangential elbow vector ("vector B"), I can argue that it is the sum of some arbitrary number of totally different vectors, with meaningless directions. It's just analytical math, neither point of view is more correct, because they both have the same resultant sum.
I contend that the workload of those 2 constant vectors is in fact being distributed across your body in a freely changing manner through the course of the technique. Thus there are not 2 specific, real forces that exist in nature that correspond to your A and B. Instead, there is a single net force at any moment in time, and it is controlled over time by you by paying attention to the idea
of these 2 vectors. Thus I said "trick." And of course I was referring to Gerardo's visualizations as well.
Doubley sorry for my complicated answer!