Current HUD system is very limited, and i have feeling that slate will be overkill for most games.
So i had idea to render all elements to texture then project it to hud material.
I would use black, unlit box with hidden camera.
My problem is how to render elements of hud for resulting material to have transparent background.
Do i need to use desaturation + power node to mask out black areas? But in this case i cannot have black elements in hud.
Maybe there is something like render distance mode that leaves background transparent without me messing with black box color.
Another way (bit more complicated) is to make HUD blueprint in 3d box and attach it right in front of active camera.
If lightchannels work like they were its possible to make it independent from light enviroment.