Even without using writeMicroseconds() you have control over what pulse width 0 and 180 translate to. That's what the min and max parameters on servo.attach(pin, min, max) control.
The default is 0 = 544 microseconds and 180 = 2400. So in your mapping terms it would be map (angle, 0, 180, 544, 2400).
If you want 700 to 2000 set it in attach. servo.attach(servoPin,700, 2000).
It's all detailed in the Servo library reference.
Steve