Your post was very interesting. And I have to agree with your explanation:
"As a result, one will be pulling uke into the kuzushi rather than pushing/guiding him/her into the kuzushi and thus into the rest of the throw. Aiki will be lost and violated."
I think the most important sentence is:
"Nage's kuzushi should commence no later than the first moment that uke has engaged his/her weight on his/her own front foot." Maybe it's similar to what I have been thinking... It's when uke*commits*to*the *strike that one should enter. In other words, even though uke is rushing full speed towards you with his hand raised, it is when he is just*about*to*stop*and*strike that one enters. If one enters much earlier than this, there is a clash of energies... or worse still, both people sail past each other
Of course, one could also move forward to close the distance (perhaps with a motion that resembles a parry), causing uke to strike much earlier
I have also been studying Doshu's demonstration of shomenuchi iriminage to better understand the timing of this waza. For those who are interested, an on-line version may be seen at:
Have a nice day