It'd rely on a bit of luck I reckon.
Back Wolves to win the tie (not to win in 90 minutes, just in case) and Southampton to win the cup on Betfair. Put more on the first bit. Separate bets, not a double.
If we lose then Southampton *could* come in shorter than 16/1 to win the cup, which is around what they're at as it stands. You'd then lay them off at the shorter price. Profit whatever happens. Bonus if someone like Bristol City gets through and they draw Saints away, they'll definitely come in then. Been a while since I used Betfair but as far as I remember it'll even show you the "green" elements of either side before you confirm it, so you know how much you win either way.
But it comes unstuck if they go and draw Man City away in the quarters because they could stay the same odds or even drift, even allowing for them being three games away from winning the tournament.
You could also add some cover as we're far too long with Unibet at the moment to win the cup. 30/1 is stupid. Put a very small bet on that in the background.
@Trips will probably know better than me.