Really? Surely the length of the fork (lever) increases the torque therefore increasing the forces and centre point of the forces?
Also disc brakes are well known for extra power, surely this fact alone increases the the stress on the frame?
The length of the lever is constant for rim or disc brakes provided some obvious givens.
For a given deceleration, the retarding force is the same.
The lower headset is the fulcrum, not the other end of the lever.
For a given force, the fulcrum receives the same force no matter where it is applied.
Further, the old myth that a disc brake has more "power" is just that, a myth. Semantics first, it is not power, but force, we're talking here. Nevertheless, no matter how good the clamping force of the brake, the bike can only decelerate up to a point where the overturning momentum chucks you over the bars. This point is well below the traction level of the front wheel so a bike/motorbike will always overturn before the wheel skids. Effectively we have unlimited traction but limited overturning resistance.
Therefore, no matter how strong the brake is, all its force cannot be used. The only way to increase braking distance on al bicycle or motorcycle is to lower the centre of gravity to closer to the level of the hub, as it is in a car. A car's front wheels can skid, a bike's not. Cars brake quicker than bicycles and motorbikes.