What happens when the manufacturer folds after the first major accident they're found liable for and now the entire remaining fleet doesn't have anyone liable for it?
If the regulators step in to remove the vehicles from the road then who makes the consumers whole now that their vehicle, and perhaps livelihood, is gone?
I suspect certification is the only reasonable path. If the regulators believe these systems are safe for the road then they should build the framework for establishing that bar. If such a framework is not possible to build then I think that also answers that question.