The Model T, like many tractors, approximates one pedal driving because although it has a hand throttle, it has enough torque that you don't have to feather it to take off. A tractor is generally set to a given engine speed for the PTO, and you choose the gear for traveling speed. Modern tractors with automatic transmissions come even closer, since road speed is governed by the pedals (one forward, one reverse), and braking is rarely needed.
One pedal driving should be pretty simple on a vehicle that does not idle, has no clutch, and needs no transmission. Or one lever, which ought to be a real boon to handicapped drivers.