Bending the brake pedal is a possible option as is removing 20-25mm from the right side. The gap between the pedals is 60mm. The brake pedal is 125mm wide and 75mm high.
I only use my right foot for the accelerator and brake, and the dealer asked me the same question. I mentioned possible options like narrowing or bending the brake pedal and he said it would probably void the warranty as it was modifying the original design of the vehicle and may make the vehicle non compliant with the ADRs.
To bend the brake pedal could be difficult as the pivot point is up in the dash, I could not reach it by sticking my arm up as far as it would go. The brake pedal arm is made from 6mm flat steel 30-40mm wide, also about half way up there is a flat metal bar attached to the front of the pedal arm going up towards the steering columm. I do not know what function that bar has.
To remove the brake pedal assembly, bend it and keep everything alinged could be a difficult task.
I might have a closer look at it and see if it is possible to remove the pedal section and replace it with a smaller one that I can change back to the original when I take the car in for servicing.
I did try operating the brake pedal with different footwear and found that it does not have much effect on whether both pedals are pressed except for thongs!. This is a car that is risky to drive whilst wearing thongs as just about every time I tested the brake pedal operation the edge of the thongs did not follow the foot across and as a result it contacted the accelerator pedal as well. Bare foot driving is the best, so when I get in the car it is thongs off and placed on the floor between the seats. So far I have not accidently hit the accelerator pedal since.