I'd love to see stack number in the hotbar standing out. Some background or font change that you'll see the stack number in any environment. Mentioned & showed it in one of my videos when pyramid building that I moved my POV around until I could see the stack number.
Something like a drop shadow in the complementary color works very well at making something visible against any color background. The same could be done for the wireframes when placing blocks, as the white outlines are frequently hidden against stone, or when there's good lighting.
