Paul Moore writes:
"Before any existing Python directories, otherwise at the end" is the closest to what I suspect most users want (certainly it matches my preferences, and anything else would have me manually editing PATH anyway, so is of no use to me in practice).
Unfortunately, what is "no use to person X in practice" is a function of X. I suspect that's why this hasn't been done. Specifically, it seems to me that there are use cases for each of 1. Append (eg, if both python3 and python2 provide "python.exe", for experimental use of python3). 2. Prepend (actually, not a use case; just common, and therefore "intuitive", practice). 3. "Moore's rule" (put latest and greatest ahead of other versions but not interfere with previously installed apps). Maybe it should be user-configurable.