BTW, I think the OP has two different ideas mixed up:

1. maximum braking force, or deceleration-rate is ultimately determined by total traction of front-tyre. The brakes only supply the friction to re-tar.d the rotation of the rim so that the tyre pushes back on the ground. Ultimate braking-power is then limited by the front contact patch. Larger contact patch from using bigger tyres at lower-pressure will give you faster deceleration. A long-wheelbase bike with low C.O.G like a touring-bike or MTB with fat tyres are much more stable and allow you to brake faster than most road bikes (given same total-weight and brakes).

2. lever-force required to generate any given deceleration-G is what the OP is talking about. This is a simple matter of leverage, the ratios of lever-travel to caliper-travel. Along the way, cable-friction/compression and brake-caliper flex may rob some of the lever-force generated at the levers. Personally, I've found the Dia-Compe BRS cables with rolled smooth surface inside teflon-lined housing to transmit lever-force to the calipers best with minimal friction and flex. Brake-pad compound also plays a big role in how much friction you can generate at the rims for any given lever-squeeze force. The soft Kool-stop pads generally gives the same friction & stopping-power with 25-50% less lever-force than most stock pads.