The trusted party there are price oracles. Plus, matters are muddied by the "governance" usually built-in which adds another trusted parties who are supposed to do emergency interventions (like Fed does ;-)

I don't mean to be mean, but if you have a fundamental security issue, "solving" it with a complicated protocol that still has the same security issues deep at the core, sounds like "scam" to me. Venmo, PayPal and Bitcoin are fair in their offerings: you know who you trust with what and that's the security model without any sugarcoating.