I'm loving the new CSS Grid feature, but I'm running into a limitation with responsive layouts and how Drupal blocks things together. To explain one use case simply, I have a right sidebar that breaks into two components, a search form and advertising. On tablet and desktop, those should be stacked into the same sidebar. But on mobile, I want to break that search form component out and put it above the content. I put together a wireframe example that shows how things move around. However, when I start to put this together in Drupal (8) with blocks, regions in my custom theme (which I made as a subtheme of classy), Drupal organizes them into nested HTML divs and other elements (ASIDE, MAIN, HEADER, etc). So the question is do I scrap base theming and keep things really really flat, like in the wireframe example, or is there a way to get a sub-element into a parent grid area, or do I need to delve into subgrids?