One thing to keep in mind is:

  package looks for python via configure.
  package adjusts itself to work with that version.

So from a binary package point of view, I think it's important that if
a package found python X at package building time, it continue to get
python X.

#!/usr/bin/env python
is a problem because if some user has python version Y in their $PATH,
then when they run an installed pkg it will execute with Y instead of
X.

So while I see the point that it's inconvenient, I agree that script
paths must be pinned at packaging time.

-- 
        Greg Troxel <gdt@ir.bbn.com>