Absolutely. One benefit of the transformation layer is that it allows you to grow the language. It could eventually be completely self-sufficient, but you can start with the hard/interesting parts, and other stuff can gradually be abstracted away.
As an example, ac.scm has a comment that ar-gensym is a toy implementation. I don't need to do toy implementations because I can just use PLT's gensym directly until I decide to build my own.
