The simplest method for Spain to regain some public confidence in the property market is pass legislation making buying off plan properties illegal.
I know this will not help people who have suffered loss. They should be compensated and a condition made that financial support to the banks both by central government and the ECB be conditional upon them (the banks) honouring their guarantees.
Trying to influence the Spanish government however or expecting justice from the courts is I am afraid like knitting fog. Impossible.