Last night I thought about this as I brewed. I think I've been lowerish oxygen brewing for a while. I heat my mash water before adding grain. That drops the O2 somewhat. I make an aluminum cap (with drain holes) for my mash/Sparge because my mash tun is a SS kettle with recirculation. I stir as needed but not excessively. I pump it to the BK without much splashing. I boil everything 60 min (thanks to Marshall's DMS xBeerment). I chill rapidly and transfer to fermenter without much splashing. I pitch after oxygenation but immediately after. I purge my kegs before and after transfer. I don't use SO2 but since last spring I've been using brewtan B in mash and boil in my light colored lagers.
I still have copper. I've heard several authorities, like Bamforth, say that it's good to have some copper.
I pitch yeast that is in exponential growth phase.
I think there is room for improvement, it's not like all of my beers are 50s. But most of them are as good or better than most of what I can find commercial around here.
I might try some SO2 someday. I recall Bamforth saying it could help with flavor stability and that most commercial breweries who don't use it, don't use it because they would have to label it as containing sulfide. If I recall correctly... it was a Brew Strong interview and been a long time since I've heard it.
In short, I don't doubt that limiting, or even completely removing oxygen, starting with the grain in the sack, all the way through to pitching yeast, would have a positive impact. I mean, what's the argument for the need for oxygen in the mash or boil? Is it the BEST way? Technically, I suppose it is. But couldn't we argue that technically, the LODO method isn't BEST either, since there still is "some" oxygen? If we want to get really pedantic about it the BEST way would be to brew in an oxygen free environment. But who wants to spend brew day in an SCBA? Not to mention we would need to go electric because propane needs oxygen to burn.
I agree with limiting oxygen where you can and to the level that is reasonable for YOUR equipment and budget.