Comment 16 for bug 991493

If you don't understand why, then there is no point in you not providing an alternatives in the package(s). The only reason for not using alternatives would be to force your viewpoints onto your users, which you should be doing even in cases were you are absolutely positive doing this would break things. Sine any tarball downloaded could potentially need(even if the need is broken or incorrect) the old LLVM even if the new LLVM is installed or Vice Vese, then this become an essential feature.

Since all you say is that thee is no reason for an alternatives and no reason not to implement alternatives, I don't understand any hesitation.