There already is some random failures in NASSP, mostly some older code. Just activate the "Damage and failure simulation" under Parameters in the Orbiter launchpad. It is mostly switch failures to do with the sequential systems, but also Saturn engine failures and launch vehicle IMU failures, which is what makes a Saturn takeover by the crew necessary. It's not a good system right now and I am planning to give it an interface in the PAMFD so that you can schedule failures, increase the chance of failures etc.