Who is to say that Einsteins theory (you call it mere unscientific opinion) that there is some intelligent creative force behind all that is the universe or interwoven into it will never be measured?
Well, I'm confident it won't be, but that confidence is not itself based on science. It's a spiritual awareness thing. So, speaking scientifically, there is no way to be sure that we won't discover such an intelligence eventually. The fact remains that at this time, there's no evidence for it, and no reason to include it in any evolutionary models.
And that still brings us back to what existed before the big bang? How did it get there? What caused it to become the phenomenon that we call the 'big bang'? And who is to say that whatever forces existed then have no bearing on what exists now? Or that such questions are not within the realm of science?
As I said, the Big Bang was the start of time, not just space, matter, and energy; there was no such thing as "before" the big bang.
We can play around with ideas like that all we like. The fact remains that there is no evidence in support of them.
In fact, I'll give you a perfectly sound speculative concept of intelligent design if you like. What if the universe itself, as a whole, is intelligent, and has the ability to alter the probabilities of indeterminate events? (There is evidence, although not conclusive evidence, for the existence of such a probability-shifting quasi-force in the study of psi phenomena.) What if the universe has a purpose in the evolution of intelligent life, and adjusts the probabilities of indeterminate evens such as the emergence of life and the course of evolution on planets throughout its cosmic body? The process of evolution would then be exactly as biology describes it -- mutation shaped by natural selection over the generations -- but its indeterminate course would be shaped by the mind of the cosmos through shifts in the probabilities themselves.
Is there anything wrong with this idea? On the face of it, no -- but neither is there any real objective evidence in favor of it, and so there is no reason to include it in any scientific theories. It remains speculative only.
The problem with ID as a scientific claim is not the claim that it COULD be true, but rather the bogus claim that, due to flaws in evolution theory it MUST be true. That's simply not so.