Signal on top of PWR line
It is not at all clear why you think your circuit ought to work, but I'll give it a try. You seem to think that by passing a pulse train through different low-pass filters, you can change the frequency of the signal, and then use zener diodes to convert this back to a pulse train. The simple answer is, no, you can't do that in any useful sense. You might try something like this, though.







simulate this circuit &ndash; Schematic created using CircuitLab

The "additional circuits" would look like







simulate this circuit

The high duty cycle maximizes the effective power supply voltage to the additional units, but between the FET IR drop and the diode drop in the final stage, I doubt you can get better than 4.5 volts for an initial 5 volts supply. Depending on what components you use, the drop might be as much as 1 volt.

Note that this approach does have a big drawback - EMI. By chopping your power supply voltage you pretty much guarantee that your system will radiate like crazy. Shielding, both of boxes and cables, will be important.