is there a way to have the wah automatically turn on without depressing the toe switch?
To explain it differently, if you are playing without the wah, and you simply move the expression pedal and the wah automatically turns on for the amount of time that your foot is on the pedal. Lift your foot off and within a set amount of time (2 seconds for example) the wah is turned off.
Morley wahs can do this, as well as the 95Q from Dunlop. As well, I have seen a G-System with this type of set up.
If so, I would get another expression pedal and have it as a dedicated wah that only activates when I move the pedal.