Positing "highly intelligent AI" as a solution to brain uploading basically says "you know that implausible bit of science fiction, let's solve it with another implausible bit of science fiction". Until you can demonstrate the plausibility of super-AI, you can't propose it as a solution to a similarly implausible problem.
"Implausible" might be the wrong word--my point is, you can't say some fantastic future technology we have no idea how to build is possible by saying it'll be enabled by another fantastic future technology we have no idea how to build, because that doesn't really get you any closer to the solution.
