You did not explain why it is *impossible* for you to use any of the other solutions. In any case, I looked at the C code. It defines delimiter (as well as quotechar and escapechar) as a single unicode char. This is different from Python which does not have a char type but uses strings (arrays) of length one as a substitute. Redefining delimiter as an array of unicode chars, as you propose, would complicate the code. It will take a much stronger case than one person's 'It would be nice' to motivate someone with the needed C skills to do the revision. It would as least slightly slow down all single char uses. It would be easier and more useful, in some ways, to write a Python csv version.

You might look elsewhere for an enhanced csv reader that handles multi-char delimiters. Searching just pypi for 'csv' returns perhaps 50 hits. If you really want to pursue this for the stdlib, follow my suggestion of posting to python-ideas and reference this issue.