Wasn't the entire point of the post 2008 banking reform to make sure that banks can remain solvent in times of need. MBS's required a 20% capital ratio at MINIMUM.
In a $5T market that is $1T in capital, banks are struggling to meet requirements in the mere billions,
And you think they are going to be able to do this on $5T?
I can assure in 5 years, banks are not going to come up with $1T in capital, they cant even raise $10 billion.