I appreciate what's being said, but here's my take on it:
I believe the idea of irimi in every move is correct in a mental or energy sense, however, not in a physical sense.
Physically, if you enter then tenkan, it's actually a "kaiten ashi" which begins as irimi, but not as tenkan.
Also, I think there's a critical problem with tenkan-ing with a physical irimi in mind: you lose a "beat," by doing so, and in a fast attack, that beat can mean missing the connection. (although one can argue if the energy flows past you that fast, no harm, no foul. Problem occurs though when you're directly in the way of that energy, when you could have pivoted out of the way by simply turning on your foot.
I've noticed that when moving, many aikidoists/kas will move their foot slightly back before stepping forward, kind of like cocking a gun, or winding up for a pitch. I try really hard to move from where I am, as the "cocking" motion can reveal intent and intended direction, plus there's that lost part of a second as well.
Ideally, there shouldn't be "slack" with proper ma-ai observed, and perhaps this slack can be stretched out while in motion, and through a turning/rolling of uke's wrist, elbow, arm, etc., which in a small circle will take slack out of the shoulder/body and help produce/maintain the kuzushi as well.
So, I'm with you 100% on the mental irimi and ki-joining with center (as Nadeau sensei says, "Centers hang out together."), but I think a physical try at true entering could lead someone astray if they generalize it into their practice, and perhaps lead to injury.