The whole point of counter rotating pairs of motors is that they counteract eachothers torque and keep the craft from rotating. If youre gonna do a glow engine, why not just have 2 counter rotating props in the center. It becomes more of a helicopter then, without a tail rotor of course. You could do 2 things i guess at this point, have small thruster motors like you said to control pitch and roll, but more likely you'd just use servos at the main rotor just like a heli. Basically this accomplishes a flying platform using counterrotating rotors, one on top of the other. I'm sure you've seen those models around, or even those post WW2 prototypes that dont have tail rotors.

One Large prop (or 2 in this case) is surely going to be way more efficient than 4 small ones, and more stable too. One thought I had is if youre gonna do a main rotor and skip the outside ones... why not put the motors at the end of big prop blades. Because the power is coming from the blade itself and not the body of the heli, theres no torque, no need for a tail rotor. It doesnt take much force to turn a blade. Pretty interesting idea really