The 6502 inside the VIC-20 can of course address 64K. However, you already have 20K of ROM (Basic, Kernel and characters) and a few I/O slots (which can be filled with RAM/ROM, but it is very unusual). I think the 64K expansions worked with eight slots of 8K each, or maybe four slots of 16K mapped into the same position all the time. You would do the bank switching manually.
The C64 has a 6510, which is a 6502 + I/O port which allows it to switch out the Basic, Kernel and other stuff. Behind these ROMs, 64K of RAM is hidden and ready to be used (well, in practise about 62K is useful). I'm not aware if there are any hacks to put a 6510 into a VIC, but maybe with a modified Kernel, it could work? Again, you would develop an unique machine potentially incompatible with everyone else.
My cold is one week old, but since I'm in front of a webcam all day, I like to make disturbing gestures once in a while and capture those moments.