Zvex Tremolo Probe / Single variable resistor volume pedal

[Johannes]

Was looking into Freds proximity wah project today:
http://revolutiondeux.blogspot.de/2008/03/vsex-wah-probe-probe-controller.html
It basically allows you to control a parameter of any effect with a distance-sensor-antenna-thingy. I'm considering combining wha, volume and maybe even expression with just one antenna. The wah was straight forward, and expression too. However, I am not sure about how to make the volume circuit. A passive volume pedal (would be sufficient for my needs, as it will be bypassed when I'm not swelling) uses all three lugs of a trimpot, making two resistors change. However, with the probe controller, I will only be able to change one. Any ideas how to crack that?

So, my request is
1) How to make a volume pedal using only one variable resistor, or
2) A vero for Zvex Tremolo Probe

[Johannes]

May have just found the circuit I'm looking for:
http://www.freestompboxes.org/download/file.php?id=17296&mode=view
Isolating the part from the volume switch to the 560 resistor should give me a volume pedal controlled by a single LDR, right?

OR

Is the 10K trimpot and LDR enough to control the volume? Could I build a passive volume pedal using only those two parts? (Plus a preamp, like LPB1 or SHO)

Sorry, this went from a request to a thread. Maybe I should post it at freestompboxes instead... :P