As Motorollin said, I think what you are looking for is just a PC with a modern DVD/CD drive. They seem to handle almost anything. Any strange formats could probably be sorted with downloadable codecs? As long as the disc information can be read and understood, then the software will play it.
Your idea of a stand-alone unit would only come in useful when the disc format itself changes and the drive has to be changed i.e. BluRay, HDDVD or the next generation of disc but then we are back at the PC and a brand new DVD/CD/BluRay/HDDVD drive.
