Yes! It is the ones who support natural evolution who make the claim that such molecular systems evolved in the past by numerous, step by step modifications of precursors. As that is essentially a historical claim, at least reconstructions of the actual pathways and assemblies would be warranted, supported by detailed, testable data, and failing that, at least detailed, testable alternatives. If Behe has performed no other service, at least he has provoked some biologists to try to provide a detailed Darwinian accounting of these molecular systems. Darwinists should be be glad for such challenges that provide even more opportunity to demonstrate scientifically the truth of their hypotheses, but I don't see much evidence that many of them are. Quite the contrary.
Where would this end?
When does science and the quest for knowledge end?
And how do you propose to discount the argument that the Designer may be intervening in the petri-dish?
What is that argument?
Cordially,
When does science and the quest for knowledge end?
Well, actually it ends the moment a supernatural entity can be undetectably altering the results of observations.
Anyway, your answer sounds to me like you just want carte blanche to propose forever that any system whose pathways haven't yet been demonstrated might be IC, and therefore naturalistic evolution isn't yet acceptable to you. That amounts to you setting a bar for the acceptance of naturalistic evolution that can never be overcome.
"And how do you propose to discount the argument that the Designer may be intervening in the petri-dish?"
What is that argument?
The argument that we've had before. Once you propose that a Designer of unknown motivation and powers can undetectably intervene, then how can you ever trust the results of any naturalist experiment. If BF appear in the petri dish, how do you know that your proposed Designer didn't tweak them into existence? Or are you going to set limits on the Motives/Power/Detectability of your hypothetical Designer?