Unfortunately, I can only write code in Assembly. It is quite easy to program an MCU to drive a logic-level mosfet to do what you want. If you don't have programming experience, I would recommend getting a controller for a few dollars and concentrate on the PWM generator, which is usually a 555-based oscillator, but any Schmitt inverter will do.
As you might imagine, model aircraft prefer a softstart, as the instant torque of an electric motor can overload the airframe and the controller.
John