Python 2.7 is in feature freeze, so this can only go into 3.7.

I would find this useful, and would like this feature. However, I'm concerned by your comment that you fall back on creating a normalized copy and comparing. That could be expensive, and shouldn't be needed. According to here:

http://unicode.org/reports/tr15/#Detecting_Normalization_Forms

in the worst case, you can incrementally check only the code points in doubt (around the "MAYBE" code points).