Hi Marin,
I won't integrate that soon in the engine, but i think there are many tools that can do that for you.
I have a "Graphite 25" small keyboard, and it has zones that have their own midi chanel and can do that very easily.
Or you'll have to tweak the code. MidiDecoder.cpp => midiEventReceived() => case MIDI_NOTE_ON.
If you have some programming notion, you can easily split the keyboard to fit your need.