The reason that this was done was to give us flexibility in deciding how the backslashes should be interpreted in the future. I announced it on python-dev here: https://mail.python.org/pipermail/python-dev/2016-August/145979.html. That message contains a link to the python-ideas discussion that precipitated the change.

PEP 536 is one proposal to change how this is handled. I don't entirely agree with it, since I think allowing:
f'Magic wand: { bag['wand'] }'
would be confusing and make life more difficult for simple (regex based) parsers to skip over f-strings.

Notice that in Jupiter (https://github.com/jupyter/notebook/issues/2037#issuecomment-272466046) and in CodeMirror (https://github.com/codemirror/CodeMirror/commit/c45674b11e990fe37abc662b0c507d3bb1f635e7#diff-04f7f1f1bbbab888742c7e849187a79c) they were able to make simple changes to their parsers and "support" f-strings (for some value of "support": mostly not break in the presence of f-strings).

However, I'm not completely opposed to revisiting the issue. Your use case is certainly a compelling one.