This is a variation on Tom Bliss's suggestions, I'll try to keep it simple:
Another way to approach the foot-pedal system is: rather than looking for a pedal that will actually create your two separate sound requirements, get an A-B switch box--inexpensive and simple, and use it with a two-channel amp, or into two separate channels on the PA. The A-B can be used in either signal direction, all it does is provide (in this usage) a single 1/4' input and your choice of two different 1/4' outputs--the simple footswitch toggles the sginal between the two outputs. So, using my example of a two-channel amp, I'd run one patch cord (the A switch output) to channel A on the amp, which is set for the lower-volume, clean sound, and the B switch output to channel B on the amp, which has increased volume and way more mids (my Peavey Ecoustic 112 has a full EQ setting for each channel, nice option) for that big fat solo sound. Once you get the sounds set on the separate amp channels, (the advantage of using your own amp is that you don't have to explain every facet of your sound requirement to the tech, just set up your amp the way you like it and jack the amp into the PA if required.)

I use a B-Band combination pickup, but really only use the piezo portion of it.

The whole other route you should look into is CONDENSER MIKES. I have a Shure SM-137, which is always on (because its the sole amplification for my mandolin), so the final guitar sound is a blend of the pickup sound and the mike. (No feedback issues with the mike, which is one major reason why condenser mikes have become so popular with performing instrumentalists.)

Hope this helps--lots of ways to wound your wallet but the A-B switch is the cheapest if you already have an amp...mine cost about $30 Cdn. The SM-137 is about $200 Cdn and it was money well spent.

W-O