The current bus converter takes an analog redstone signal and converts it to a bundled cable signal where each power level activates a different line in the bundled cable.

But given that there are 16 lines in a bundled cable a cable can theoretically support 4 separate analog signals if you instead treat each of the 16 lines as a binary bit. 0 to 15 is a 4 bit value so the first 4 lines would be channel 1, the next 4 would be channel 2... etc.

You would then just have a new bus converter that can be switched between the 4 channels.