This is why I think it is a bad idea to generally promote the use of the individual components at this time. People are still free to use the components but given the resources committed to the core I don't think this is something we can reasonably support. All the IDE integration uses the embedder, the Ant Tasks can use the embedder and I don't see any client use that can't use the embedder. Yes there is a reasonable hit in the size of embedder but is the best way forward with respect to giving people a usable externalized form while giving us the change to improve upon the internal APIs that we would ultimately like to expose.
I don't think it's impossible to start promoting these three APIs in their proper place right now. It would take us all of 30 minutes to wire up an aspect to the maven build which would "hide" the ugly apis from the outside world, and only expose those apis we have written to be entry points. We don't need to restrict a "Read/Write POM" public API to the maven-embedder project right now, for instance. We could easily aggregate all *.public packages into the eventual embedder jar, too, so this is available from there...but it doesn't need to be restricted to there.