Depending on how old you want to go with the interfaces, it may be easier to start with an older ISA bus based PC and adapt new technology to it. The older could handle 3 1/2 and 5 1/4 media already built in. Going to card reader style input could be configured to a serial or parallel port. For tape drive interfaces there were a number of special PC boards on the market 20 years ago to interface PC's to reel-to-reel drives. Then you would need to add an interface between the older bus structure and the USB to open up remaining devices.