From the brilliant ideas that will never work file: mortgages where you can
revert to any previous amortization schedule.

Suppose you have a mortgage. Suppose you unexpectedly come into a
significant amount of money, and you promptly to pour it all straight into
the mortgage. Then suppose that shortly after this occurs you lose your job,
and don't have enough money to make your mortgage payments. Under the
current system, I think you can reamortize, or you might be able to
negotiate skipping a payment, but interest would still accrue.

Under the proposed system, you would have the option to return to any of
your previous amortization schedules. You could look at a previous schedule
and say "According to this schedule, I should have paid $75,000 by now. In
reality, I have paid $85,000. According to this schedule, I'm not expected
to have paid $85,000 until five months from now. Therefore, I'm going to
stop making payments for five months." No further interest would accrue over
these five months (because you're all paid up, right on schedule), and after
the five months have passed (giving you time to get a job and get back on
your feet) you'd resume paying according to the previous amortization
schedule as though nothing had happened.