Our waza is currently in the toilet. That said...
I am not a fan of irimi nage. I actually think 2 judo throws (o soto gari and koshi guruma) do a better job of showing the jujutsu of what is going on. When I first started seeing the "uke turns into nage and gets split over the hip" throw, I remembered thinking, "isn't that just a funky koshi guruma?"
Here is a link to some koshi guruma samples:
Some o sot gari samples:
So what's make irimi nage different? I guess...aiki...
I tend to think about the chokusen no irimi nage as my irimi nage; a direct entering throw with no tenkan. If you can get that guy, you can making a pretty turn and do it, too. I think irimi is vertical separation with lateral expression. Both Tissier sensei and Ikeda sensei often show very large vertical movement and very clear body rotation to illustrate the vertical separation and lateral movement.
I am not sure grabbing is particularly helpful. I tend to feel like the grip is more to stay connected to a partner you are throwing, not contribute to the throw. Ultimately, I think you are separating your partner's spinal alignment through vertical movement and using lateral movement to create kuzushi. Aside from relative position - I am not sure we're talking much difference from ten chi nage in terms of principles, only the lateral movement.