Yes, but can't we still just accept it as plausible?

That's not how plausible works. I could say that I don't think that life on this process began with chemicals and random time like all the scientists doing real work on the subject actually think. But I think humans from the distant future traveled back in time and created this planet and invented the life on it.

Would you argue that is plausible and credible and open? Do you think there being no evidence against it or for it, is a mark in it's favor?

The answer really should be no. I can with enough special pleading make the claim that the moon is made out of green cheese something for which there is no evidence against. We know the density of the moon, well the cheese just happens to be very dense. We've been to the surface and found rocks, because it has rocks on the surface. If I explain away every objection with another bit of story I can get it to the point where we should find no evidence against the proposition of our moon being made out of green cheese in some kind of special way that makes it outwardly appear to be made out of rock.

Should we then say there's no evidence against the theory and at the very least we should consider it plausible and credible?

The actual answer is no. Evidence is largely defined by Bayes Theorem, and there are a few variables there for how ad hoc the hypothesis is and how much additional stuff you need to accept it and how good the alternative hypotheses actually are.

This is the case with Hameroff's theory. We should not consider it plausible or credible because it is stupid. It is trying to explain away a robust observation that our consciousness actually becomes aware of decisions our brains have made half a second later. It invokes utter crap that physicists and neuroscientists scoff in an attempt to explain these observations away. But, really we should just accept that those observations are true. The moon just happens to look exactly like it's made out of rock because it's made out of rocks. And our gap junctions have chemicals and only get triggered by chemicals and our brains consist of neurons firing in patterns because that's what we are, neurons firing in patterns. The truth isn't something that needs to be explained away with exotic explanations, it can actually just be true.

So, no. The fact that it's really absurd is actually considerable evidence against it. And the fact that the alternative is that what we see is what we get, and that explanation explains all the data that needs explaining suffices to say that a theory that needs to make thoughts exist in quantum fields and magically travel backwards in time, can go ahead and be discarded as wrong.

You may not solve the mystery of missing socks by involving elves. Elves are a greater mystery than missing socks. Socks go missing. You don't need to explain how because of QM they fell out of the universe and traveled forward in time and we'll end up getting them back. They really can just get lost. Brains really can just be a skullfull of neurons and chemicals. And the moon really can just be rock.