Right now there are basically two paths in Replace in Files, one that does a set of replacements in an in-memory Document, and one that does a set of replacements on disk. The Document version should be functionally the same as what single-file Replace All does today (mine is actually a little dumb right now since it sorts the matches in reverse order instead of just assuming they're already sorted, which is probably true, and reversing them directly). I can figure out how to merge the two when I hook all this stuff up to my stuff.