Uncertainty about what the original autographs said is no argument against inerrantism about what the original autographs said, not just because whether the original has errors is independent of whether we know what the original said. Kenny Pearce offers some Bayesian probabilistic reasons for concluding that a doctrine of inerrancy might still make a difference epistemically about particularly propositions despite uncertainty about whether the original autographs teach those propositions. He applies this to doctrinal issues that inerrantists who accept some principle of sola scriptura might nevertheless dispute, and then he applies it to science and evolution. I don't really know any Bayesian probability, so I can't really evaluate this in those terms, but what he's saying seems right to me in general.
I've cross-posted this at Prosblogion, so you might want to check the comments there to see if it generates a good, higher-end philosophical discussion.