I don't see any appeal in stick figures whatsoever, and I would avoid using the line tool as it'll probably make them look even worse, but..
Try this: draw your character, getting the proportions as anatomically correct as possible. Now, create a second layer below it. Using a very light color, draw a horizontal line across the stage at the bottom of the characters feet; add a second one at the top of the characters head, a third at the characters neck, and a fourth at it's waist.
Lock the layer, and use it as a guide along with the onion skin feature to keep your character's proportions consistent throughout the animation.
