The process of converting stompboxes to modular has been going on for quite some time now. There is also a wealth of information online on how to get started if you know where to look. Ken Stone's Stomp Box Adapter PCB/schematic is a good place to start but this one is for the 5u guys. The Music Tech DIY forum on MuffWiggler has a wealth of information too!
The main issue you may run into when attempting to do a conversion is that modular synthesizers generally use a much higher sugnal level than a guitar effects pedal. So to compensate the signal from the synthesizer must be dropped to a fraction of what it was, while the output of the effects pedal must be amplifed by the same amount to restore it back to synthesizer level.
The other issue is that most guitar pedals run on a 9V DC power supply, whereas Eurorack runs at ±12V DC so you will need to make a DC-DC convertor circuit to compensate for this.
Generally speaking we think it would make sense for guitar companies to consider doing this to some of their pedals. Or maybe just add some CV inputs.
Here's another example of the EHX Big Muff modded for Eurorack by Matt
If the modular world continues to grow at the rate it is at the moment, surely it would make sense for guitar companies to start doing this...? What do you think?