Do you think causally pouring the new wort in would oxygenate enough, but not too much?
I have zero experience in this area...just brainstorming/thinking aloud. I personally would fear doing a direct pure O2 injection since there's already a large yeast colony, and staggering additions of 1.200 wort will dilute its gravity a lot...probably won't shock the yeast with osmotic pressure changes. I'd think a splashy pour into the primary would give just enough O2 without causing oxidation.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10