I'd like to see an easier/more streamlined way to buy minerals from the structure build tab for planets instead of having to close the planet window, go over to the trade tab, buy a bunch of minerals, go back to the planet window, find my planet, open it back up, and then build my structures.

There is... Use 2 browser tabs...

I agree though, it would be nice if the game would automatically purchase the necessary minerals for buildings or ship modules if you don't have enough in your hold. I believe this has been brought up before...