Well, off the top of my head....

You could make the frame of the kite rigid, and apply the fields to that, so that way your dynamics solve a little faster.

For the actual kite cloth, depending on the material you want to use, (meaning cotton, linen or plastic etc.) you might be able to get away with using either blends, or sdk's maybe?

Just ad a ripple deformer to the middle parts of your "cloth" material and base the noise and/or magnitude factor of the ripple on the Kite frames' translateY?

That way, as the kite gets "blown" up into the sky, the ripple gets stronger, and as the lift slows, down, the ripple slows down as well.

On the topic of the string, I'm not sure, but there is a melscript on highend called: FixedLengthCurve found here: https://www.highend3d.com/maya/plugin...animation#2125
You could maybe try using that as your "string" and make it a goal for a softbody extruded strip of NURBS material, mapped with a 2d string texture......

Just a few ideas