I definatly would like the option of a global layer :)
My current approach for bigger projects:
I use dedicated layouts as object holders and an event sheet called HUDevents, which builds a desired hud on a uniform layer named HUD.
When using dedicated object layouts, I came to find that splitting it up really helps here too.
In one of my subfolder of layouts there will be a HUD folder, with a dedicated objects layout for every needed hud type.
Here I can mimick/duplicate the desired effects my HUDevens sheet would build on start of layout once included on any desired layout.
Prevents clogging up my layout editor too and keeps my HUDs very managable.