x86_64 is multiarch. That means, we allow both i386 and x86_64 binaries to coexits. Is the proposal that python should not support this? That would be unfortunate.
The problem is that at the moment, a package has to live all in one place. This doesn't mean you can't have both types of binaries for python as a whole. (Though whether you can run them in the same process is another issue.) It does mean that you can't have them in the same package.
This is already awkward for packages split between python and extension modules.
As a workaround, you can add a .pth file; eggs and namespace packages may improve the situation some more.