I have been thinking about ways to do this, and the one thing that worries me the most is oxidation, any thoughts?
I think a lot of homebrewers think about oxidation the wrong way. Air is not very dense, and a few pints of air don't contain much oxygen (around 0.1 grams of O2 per pint, if I've done my math correctly). Oxygen is also not readily soluble in a still liquid, it needs a lot of surface area to start to dissolve (this is the reason for oxidation stones and splashing to get O2 into beer). The real problem is if you have a leak that air can move through or a membrane that's slightly permeable, then you can get a lot of pints of air.
I think you could purge a torpedo with CO2, then quickly connect it to a beer line, and although some oxygen would get in it would likely only be tens of milligrams.