Oh, but I would consider this to be cheating ;-)
I mean the temporary replacements. Your solution reduces the complexity instead of mastering it.
Of course I agree that this often is a good strategy but I was curious if it is possible to handle the three tasks (unescape, conversion, different treatment of escaped and unescaped metachars) at the same time, only allowing a little pre- and/or postprocessing perhaps.

But still, thanks for joining in!
-Michael