why couldn't we provide 'mppe-kernel-source' instead of 'kernel-patch-mppe'

["Li Daobing" <lidaobing@gmail.com>]

Hello,
I want to know why we don't provide 'mppe-kernel-source' instead of
'kernel-patch-mppe'. If so, I could only build the mppe module instead
of build the whole kernel.

Thanks
Li D.B.