I don't care that much for schema as I'm not an ORM writer, but I do have used Datables a lot as a convenient data-mangler type for importing legacy data, converting data etc. They may be "dirty", obsolete or whatever but they get the job done.
I read it all. Seems like schema is more-or-less getting taken care of.
But I don't get the big problem here. If someone _needs_ DataSet/Table, why don't they just pull in the reference source or Mono? That beats bringing that into the new Core API and avoids bloat. If it turns out it's too critical, put it in 1.1 or something.
Mono might work, but the reference source license doesn't permit you to do what you suggest. You can't copy the reference source code into your project and use it. They're very specific about what "reference use" means.