You'd have to resize the textures manually before adding them to an atlas. Atlas accepts final textures in the size that they're meant to be in.
Just wondering if there's a Q&D workaround for this at all?
We have a large atlas for one particularly art heavy menu. The game is being developed for console and handheld and at full rez the handheld has a tendency to run out of VRAM on this particular menu (the main UI atlas is in memory permanently, but this one is loaded and binned as needed).
Because we're work in progress I'm loathed to keep 2 completely separate sets of textures and atlases in the project (given they are likely to get tweaks). I assume the reason scaling the atlas in unity breaks the UI is because coordinates are set by pixel. Just wondering what the implications would be of offering an option to convert the coords to a UV scale 0 to 1? If you know what I mean