I'm not saying it's right, but hypothetically, could this work?
When banks and Building Soc's start ramping up their interest payments could people who want to get off the mortgage merry-go-round walk away?
If banks were not being fully honest or open* about their financial situation at the time of drawing the mortgage, customers might argue that they should not now be expected to pay what is in effect an interest premium on the banks poor lending policy, which was concealed at the time of taking the mortgage.
In effect, the lender made it impossible for the borrower to know the true extent of their financial health or otherwise. If an informed decision ("do I want to deal with this company?") is impossible, does that nulify the contract?
(*for example, in its last annual report EBS only had property loans of €512 million on its books, however it seems they are now seeking to transfer loans of €750-800 million to NAMA.)