Prolly the one thing I’d do is some color correction, boost the saturation a little bit and use some curves to boost contrast, get some richer tonality in the shadows of the clouds. But that’s just post stuff, good job getting the shot!
Re: Getting a longer exposure… I think it looks perfect. When I’m shooting the sky I actually prefer using a darker exposure to get more highlight detail out of the really bright parts of the sky around the sun. I set my camera’s exposure compensation to -2 stops. I can easily bring the dark parts back in post, especially if I’m shooting RAW at ISO 100. You have so much lattitude in the shadows and barely any noise, and the extra detail you get in the highlights makes it worth the work.