Perhaps a mixer would suit your needs better than a new multitrack recorder. Much of my work these days is documentary style for television, and we go straight to camera from the mixer. Boom hard left, radios hard right. The multitrack is usually left in the car. You can source a 2nd hand sqn or 442 for well under 1k.
You can always break out the h6 at times where you need isos. With the mixer in front, your dynamic range will increase, as will sound quality. A couple of 2nd hand g3s should come in at around 500 pounds.
MKH50 for indoors as suggested by RPSharman, and invest in some good wind protection for this and the lavs. If the wind is hitting your mics, everything else falls down.