Well, when you have only waves then you by definition can not have position and momentum at the same time, because they are related by Fourie-transform. So for infinite wave bunch the momentum is well degfined, but what is the position of such bunch? For short wave bunch position is well defined, but the momentum blurr is inversly proportional to the bunch length and thus is very high. Same with energy/time as they are too Fourie-spectra of each other.

Thus, description of blurry waves is probabilistic (i.e., all you can say what are chances to find the bunch here or there.)

And when you found it somewhere, what does collapse? Only lack of our knowledge (we did not know where it was, and now we do).

But there is no physical law which would limit the speed of collapse of lack (or presence) of knowledge, so it does not have to be less than speed of light. I see no violation in istant collapse or birth of wavefunction.