I see two cases, X and Y:
(X): If we pay out using the old $1/BTC price, total debt = $1 + $1 = $2, we pay out 50%.
A gets 0.5 BTC = $5 and B get 0.5 BTC.
(Y): If we pay out using the new$10/BTC price, total debt = $1 + $10 = $11, we pay out 90.9%.
A gets 0.091 BTC = $0.90, B gets 0.909 BTC.
In X, where we use the old price, the dollar holders end up with more than they were owed, while the BTC holders end up with less.
In Y, using the new higher price, everyone gets the same fraction of what they were owed.
Y looks like the fairer case to me. What does anyone else think? Can someone make a case for dollar holders to be making a profit on the dollars they were holding when the price of BTC goes up? Maybe I'm missing something.
I was in a hurry yesterday when I posted. There are more options, including the one Seal proposed. He suggested converting BTC into AUD at the current price, but allocating it to creditors at the old price. Let's call that option Z.
In Z, we sell the 1 BTC for the new price of $10, but use the old price to calculate the total debt ($1 + $1 = $2). So we can pay everyone out 500% of what they're owed: A gets $5 and B gets $5. Actually that seems to be exactly the same as (X) above, except that everyone is paid out in dollars, not bitcoins.
From a practical point of view, I'd rather pay out in bitcoins. Then I don't have to work out how to make international bank transfers, etc. Paying Bitcoins is much easier.
I agree with Patrick that (Y) seems to be the fairest option.
I suspect that if put up a claims page, some percentage of accounts will remain unclaimed. I have no way of contacting account holders; WBX never collected email address (although I expect Andre has a significant number of emails from disgruntled customers in his inbox). It seems likely that the amounts in unclaimed accounts could offset any new creditors which come to light. But that's just a guess; I have no way of knowing for sure how many customers made deposits which never got further than Andre's bank account, and never touched the WBX database at all.