[...] The only thing I find missing is the ability to install a binary distribution without overwriting the existing symlinks (e.g. ghc -> ghc-7.8.4).

I second the OP's request and Reid's one: I think the binary distributions for *nices should neither contain unversioned executables nor should they try to link these to the versioned ones for themselves. This is exactly what update-alternatives is for, and it does it in a very principled, standard way everyone understands (or can at least look up :-). Death to the not-invented-here syndrome! :-D