Quick question while I'm away from my gear...

Can you combine using a Pio DJM-850 in External Mixing mode, with using ONLY SOME of the controls on the mixer as midi only?

I was just thinking - there are some knobs/buttons that I never use (Fader Start/Mic Section) that I could map to something useful in Traktor...

Of course. Mic Low/High knobs for filters or that one smart FX that sounds so good, mic engage or talkover button for flux/sync,...