It would be very difficult (unless they are exceptionally high contrast pictures) - as the detail will most likely be gone once it's reduced to so few tones.These all look amazing! What's the possibility of getting 6 people from different photos onto 1 A3 picture?
But I'll never know unless I try - but just so you know, the waiting list has grown a bit (lots of requests from work/here over the last couple of weeks, struggling to keep up atm!) - but feel free to pop the pictures to my trust/link to them & I'll have a play around in photo-shop & see what I can do.