Seems like if you freeze the beer in a corny keg, the slushy bits all ought to be float at the top. Hit it with some CO2 and transfer the remaining liquid (the dip tube's at the bottom, after all) to a fresh, clean, sanitized keg. I know you're not paranoid about adding a little O2, but seems like that would help you minimize any oxidation. Using anything like a slotted spoon or whatever to remove the ice, seems likely you'd aerate the **** out of it.
Actually, why not do a practice eisbier run on something else first? Make a pale-ale eis or something, get the process down before ****ing around with the real deal. You know how dumb it is to try something brand new and completely unproven on a beer like the Utopias.
I don't know what I think about freezing beer in a metal corny I would intend to use again. Expansion might warp the corny making it unusable. The slightest warp in the wrong place could cause poor seals.