<<I suppose it might be a bit of a faffy job rewiring a small lightweight headset from parallel receivers to independent. You'd need at least a five-core cable (one pair mike, one each receiver and one common return) and since such cables aren't readily available you're looking at six core straight away which is a greater diameter and therefore needs a bit more room to terminate in the set. Ideally, you need tinsel cable as well which although is more or less infinitely flexible is a sod to solder and so has to be crimped, fastened, screwed etc.>>
Yes, but people are trained and paid to do such jobs, just like I was trained and paid to whack the jets into Heathrow. If I can re-wire a headset for ham radio use, with independent earpieces, then professionals ought to be able to do it!