I believe Sony tried this in the past and faced some legal issues. I believe FM-to disk was an option as well. I believe they are back in the market with a unit that does jsut this, but only holds one CD or so - I don't get into aftermarket audio much.
As for a HDD-based stereo, Dension has done this for quite some time:
http://www.densionusa.com/dh100ix_info.htm