You won’t be able to blend in a full-range dry signal because of the phase rotations of the x-over circuit. You can test it with a parallel blender pedal to hear the phase cancellations… which may not sound as bad with the fuzzed signal as it would with just clean signals.
But, it is possible to tap the low band clean signal from the x-over output, before its fuzz circuit, and blend that back at the 3-band mixer un-fuzzed. This wouldn’t be an easy mod without the schematic and layout of the circuit. You might want to try contacting the builder to have this mod installed.