My point is that 30BB in assets doesn't mean 30BB in cash. Remember an asset on a banks balance sheet is a loan lent on leverage backed by customer's deposits (liabilities) and multiple types of short/long term loans.
The more I think about it, the more I feel that the pref's and commons will be assumed by JPM or at least some some type of ratio transfer for commons. If JPM had to pay out 30BB in cash they would be seriously damaged financially and most likely just declare bankruptcy.