If I could find someone to do the design work, I would replace the PCB in my cpc464 with one that had a Z80180 processor, 4MB or 8MB ram and a hard disk in place of the floppy, it might also have an Ethernet port, 2 x AY-3-8910, RTC, light pen socket and speech synthesiser.
The OS would be Symbos with Amsdos and CP/M compatibility, and be able to copy from cassette to hard disk.