Is it possible to manipulate the time they are powered before start up?

If so, think InMotion could do so?

Would this even make cold starts easier?

Manipulation of the glow plugs is highly suggested against. The glow plug control module is controlled by a PWM signal which effectively controls the power to the GLP and thusly the heat generated. Because of the ceramic construction of the GLP, they are very sensitive to over-temp conditions. If the GLP is overpowered and gets too hot it will crack and the tip will break off, fall into the cylinder, and pistons/cylinder head ruined. Use the block heater instead.