What kind of language limitations (if any) do we want to place on implementations??

i.e. Do we want to standardize how we will implement the functionality in the Image Kit or are we free to use whatever tools we are familiar with? Personally, I do most performance related stuff with Cython, so are we ok to require Cython as a build dependency? Or would we rather limit things to python and the C api only? I guess this kind of similar to the discussion on dependencies, but still maybe deserves its own attention... Cheers, Chris