The few times I've wanted to completely rearrange a repo, It's been enough just make a backup branch and then dump the log from there and pull what I want.

I have script somewhere I think it's called git-cherry-replace, which soft resets a commit id and copies the commit message and optionally populates GIT_COMMITTER_DATE and whatnot.

What I described is probably simple enough that an LLM can implement it.

But unless you're trying to retroactively reconstruct something to preserve the exact meaning, you should consider whether a rebase even makes sense.