I am certainly no expert but do try to play this set from time to time. For the 5th and 6th full bars in no.2 Sehr innig, I play the inner part in thirds or sixth with my left hand (I am sure I saw that suggestion in an edition somewhere).
I have also given up trying to play the Noch schneller ending of no. 3 as written and redistributed the notes between my hands so that they do not get in the way of each other. This means that the phrasing (as shown by the slurs) is emphasised; the descending octaves at the end, I no longer play in one hand, but with the lower note of all except the first octave in my left hand.
It is certainly easier to get the musical effect this way.
Others might object, in which case, I too would be interested to hear their point of view.