It would probably sound better if you use a nice distortion pedal. Thing about most small (10-15W) solid-state amplifiers, they don't have good heavy distortion tones.
I use a distortion pedal through the clean tone of my small solid-state and the result is whoa. :mrgreen:
The MG15DFX is a single-channel amplifier, isn't it? I doubt such a mod is possible. If it is a dual-channel amplifier, a footswitch can be used and no modding would be necessary as the amplifier will have a plug-in for a footswitch.