Good question, but it doesn't look like you are finding many answers here. I have been entertaining the idea of a 6x42 myself, but haven't found the right one yet. Heavy mirage during the summer months usually dictates my variable scopes down below 12x anyways. I think a fixed 6 power scope with a 1/2 mil reticle, 10 mil elevation knob, zero stop, and capped windage knob would be one hell of a mid range hunting scope. Unfortunately, there doesn't seem to be a market for a scope like this.
If you could get an m5 elevation knob, low profile capped windage, and a tmr reticle for the fx3, I would pick up one up for sure.