Financial and economic cycles are inevitable. But do they have to overshoot into bubbles and crises? Once there has been a bubble, the crisis cannot be avoided, so the essential project is to work on preventing the bubble.
To address this at the most fundamental level, we should be working on countercyclical behavior to moderate the upside overexpansion. Specifically for mortgage finance, we should create countercyclical loan-to-value limits. Of course, this is the same thing as countercyclical down-payment requirements.