The way I was taught irimi nage, what uke wanted to do is irrelevant. What if instead of wanting to stand, he tries to dive and take down your leading leg? [...] They don't give uke a chance to choose what to do when his balance is taken.
If iriminage was perfect and invincible (when performed according to specifications, granted), we could all study iriminage-do, wear tee-shirts warning potential attackers that we've studied iriminage, and no one would ever touch us! After all, though it may be a bit convoluted, there's a way to find iriminage from just about any attack, right?
Uke's intention ("want" or "choice") must always
be relevant. After all, there would not have even been an attack without it. Nage must always remain fluid, connected, sensitive to the immediate conditions and ready to spontaneously adjust as necessary. No two attacks are identical, and there is no technique with a guaranteed outcome, especially with a sufficiently inspired
As for the what-ifs, that's why we learn principles, learn various techniques that apply to different situations, and learn to adjust.