You probably can chip it close to the 125i, seen the 1.6 engine also exists in higher kW variants, it will probably also mechanical rather hold good together.
But I wouldn't like to live with the uncertainty and risk. When you step on it regularly, the 125i will give you more comfort of mind that you won't blow anything. And when you would, BMW remains responsable.
Did your friend consider the step up to the M135i? When you configure a 125i like many here with M pack & xenons, it's only marginally more expensive than the 125i. When you configure such a 125d, it's even more expensive than the M135i.