I have now committed the changes to the installer. A demo installer can be found at
http://prof.beuth-hochschule.de/fileadmin/user/mvon_loewis/python-3.4.16027.msi
I'm skeptical about the lack of proper deinstallation: per convention, uninstallation of software ought to be "clean" on windows, i.e. return the system to the state it had before the installation.
Uninstallation currently isn't clean when pip installation is selected. I know this is what the PEP says, but I'm still unhappy, and I know that users will dislike it. So as a compromise, I made the installation of pip non-default, meaning that users have to opt into installing something that doesn't properly uninstall.