I just found out about the pedalSHIELD MEGA today and I was wondering that if I were to add a couple more components and change to code a bit (or maybe a lot), will it be possible to produce something similar to mfx pedals today i.e. ZOOM G1on, G1 FOUR etc.

It would be cool to be able to stack effects on top of each other...

Hi dushieet, I'm sorry for my late reply, but here I go:
The pedalSHIELD project auqio quality is limited by the Arduino (MEGA in this particular case) ADCs and DACs (analog-to digital converters and vice-versa). It is a fantastic project if you want to learn about how to code and build your own digital guitar effects.

The Zoom G1/G1 Four pedals include audio codecs ( that have better quality than the Arduino DAC/ADC) and also are programmed in a more complex/difficult coding language (DSP dedicated programming software). So simplifying, the answer is no, we cannot make the Arduino Mega into something like the G1.