I can see why you would like to get it, because you are of course impatient as we all are, and are a capable modder who may fix some of the issues for himself. And could assist Pimax in their efforts too.
But from a Pimax perspective, I can see why they don‘t want this to happen. They probably don‘t want to repeat the 4K approach, but release a better quality product because the 8K is their shot at VR greatness. The 4K would never have become that due to lack of 6DoF, but the 8K has everything it takes to be the next gen VR HMD.
If they release it now in its current state, reviews will talk about the great potential but also add a number of complaints why it sucks and is not ready for the consumers. I know some dedicated VR websites over here in Germany who are very sceptical of the 8K, and I know they will tear the 8K to shreds if it were released in such state. If the 8K is updated during the following months and ends up being in a much better shape, they will not care. Those who read their reviews will be convinced that the 8K is a work-in-progress thing they‘ll steer clear off because they want a plug & play device.
So if Pimax want the 8K to really blow away the entire VR community and get positive reviews, and it clearly seems to have that potential, then they should release it in a state which is free from major issues. It seems that this is their plan, and I think it is smart as long as we are talking of a couple of months and not a substantial delay, say release only in 2019.
But I could see the sense in having you get it into your hands now to help iron out the remaining kinks - as a nice side effect you would have the 8K at home… but I guess they would have to ask you to sign an NDA to be consistent in their approach and fair to the beta testers.
@xunshu: is this something you could consider ? This is not about beta testing, but about checking whether Pimax and Sjefdeklerk can agree to cooperate in the ongoing refinement of the 8K firmware & software. I believe he has proven his value in such process in the past.