Why not just ferment, rack off the beer and reuse the yeast cake? I wouldn't worry so much about autolysis as much as oxidation. I've brewed on two consecutive days to fill a large fermentor, but I don't know that fermenting out and then adding more wort has any positive effects.
I have an 11gal solera-style barrel for sour beer, have pulled two 3gal batches off it. GOod stuff so far, but this is sour beer not regular.