I'm not sure about the effects of diluting the greywater, but I have an alternative idea. You could build a gravel reed bed in a sealed container, big enough to store 3 days of grey water use. The biology around the roots of the reeds
should help eliminate any pathogen problems in the stored greywater, and even if there are pathogens, they would be safely beneath the gravel. You could set up a
pump that would empty, or mostly empty the reed bed into your filter and irrigation system, every 3 days or whatever your irrigation cycle is. Better yet, if the elevation makes it possible, set up a siphon so that once the reed bed fills to a certain level it activates the siphon and empties the reed bed without a thought from you. You could adjust the height of this siphon to your greywater output so that the siphon activates every three days.