Why this choice? In the case that a treatment is life-saving the ethics board can approve experimental treatments on a case-by-case basis. Medical laws just don't allow patients to make this choice for themselves.
The problem with the centralization (regulation) approach is that it assumes one body can be chosen that will be optimal at risk assessment. In practice, the process of developing good risk analysis frameworks - that strike the right balance between cost, risk and efficacy - is often best discovered through trial and error, and that requires the freedom to try new products in the market.
There's an ethics board per hospital. And there's different countries. You can in fact shop around if that's what you want to do. You can do this, both as a patient and as a pharmaceutical company. It's just really expensive.
Even a law requiring an ethics board, with statutory requirements for how that ethics board is constituted, is a one-size-fits all meta-solution, created by one body: the national regulator.
