Make it heavy and fast.

Mass is moved less by gusts, and airplanes absolutely are moved about by gusts. They don't feel the steady winds, but absolutely do feel gusts. Ever read about the crashes caused by turbulence and micro-bursts. That's the result of an airplane responding to "wind". And while you're adding mass, don't add volume because it gives gusts something to grab onto.

Are we talking about wing loading here? No, were're talking about density. Yes, wing loading is a form of density and applies somewhat, but the issue of response to gusting winds is multi-directional, and wing AREA is only important in the vertical direction.

What else?
Speed.
Make your wind plane fast.
The faster it flies, the less a 5mph gust will affect it. The better it can accelerate, the better it can respond to gust displacement and important too: it can make it back to the field in a high steady wind no matter what it can do against the gusts.

So what are we coming up with?
A model that's going to be harder to fly safely in good conditions.
It's going to be fast and heavy.
But it'll be better in gusty conditions. But then your skills need to be "better" for flying in gusty conditions so harder to fly in calm isn't exactly unacceptable. You gotta be able to do the flying if you want to do the flying.