is this pedal modification possible?

[Jacknife]

Mod a guitar distortion pedal by replacing the input and output with a microphone XLR input and output?

Would a mic plugged into a distortion pedal at the same volume be more prone to feedback?

[lumbago]

You'd be better off using a small mixer with an effects send/return buss and putting the distortion in there.

You could also buy a XLR-quarter inch converter, or a DI box, and try your method - but I think you'll find the mixer moe controllable.