It would be great to be able to change the opacity of everything on a tag. Here’s how I’d use it: I’m an architect & urbanist who regularly builds streetscapes. Trees on the streetscape, when viewed straight-on from across the street, can be as much as 50% opaque and you can see both the tree and the building behind it just fine. But if you’re looking down the street, where tree stacks on tree, then the buildings are entirely hidden because of the many layers of trees. And this varies with the angle at which you’re looking. So if there was opacity control for tags, I’d set the scene, then just play with the opacity slider for the street trees tag until it looked just right.
I’m certain there are countless other uses for such a feature. Has anyone requested something like this before? How might this feature get serious consideration?