Hey modernist, I have a suggestion based on the color-change that you're showing above.
Remember how, in the default UI, if you open the world map and enter combat, it flashes red around the corners to show that? It makes sense because you can't see if somebody is attacking you when the world map takes up the whole screen.
Well, a similar feature could be useful in modui because the world map still covers a big part of the screen. A situation might occur where the player can't see if he's in combat. (The player might have moved his unitframes to a position where they're covered by the world map, for example.)
So the idea is to make the textures of the action bars, minimap, worldmap and uniframes flash red in a similar fashion to what you show above, if the world map is open and the player enters combat.
Would it be possible to make it change the color of the UI to red, and then just turn the whiteness/blackness value up and down, and then back to the user-defined setting if the map is closed or the player exits combat?
Or maybe it would be better to make it go back and forth between red and white in the color-wheel, while keeping the blackness/whiteness setting at a level where it's possible to see the change.