Note that the VIC chip prepares the sprites at the beginning of the scanline so you can’t horizontally multiplex them.

The 3 bytes of bitmap data are loaded into a small buffer that is used up as the sprite is displayed and the buffer isn’t reloaded until the next scanline.

Even though it’s difficult to control, the cpu can manipulate the VIC during the scanline which is how you can turn off the side borders. But you can’t horizontally multiplex the sprites, that’s a limitation of the VIC chip.