Where are you going to get an appropriate set of facts from, though? You're essentially proposing a legal thought experiment, but thought experiments are notori

Where are you going to get an appropriate set of facts from, though? You're essentially proposing a legal thought experiment, but thought experiments are notorious for setting up unrealistic sets of facts to be based on - how often does a scenario exactly like the trolley problem arise, and is it even justified to extrapolate any moral conclusions from that to other scenarios? There is a legal saying - "hard cases make bad law". The temptation in your system would be to make hard cases, for the same reason hard cases are prevalent in ethical philosophy. The effect on the resulting law is predictable. So you need to work essentially from cases that have gone through at least court case. That's called an appeal, and it already exists.