Steve J. Gray is working on project to create a new VIC-20cr (Cost Reduced) Motherboard which could become a starting point for modified VIC motherboards. For example with a single 32K ram chip you would get a VIC-32. There would be possible to combine multiple ROMS into a single ROM to save board space, or add extra colour RAM, SID chip, or a different video chip, or add a second joystick port.
Steve also post VIC-20cr schematic diagram in Kicad so mage sure to check The VIC-20cr Reloaded Project Page.