Also you are correct using transparent background showed unwanted interface, if we can only find the script for map interface and restrict the HUD to refresh when near?
I aren't sure if I understand your question. The way that Spriteset_Map draw things isn't that simple. Essentials connections load maps when you are near, so the HUDs (since there is one per Spriteset_Map instance) are already drawed only when you're near.
The solution is to change the way that the HUD (or pictures) are loaded, stopping using the Spriteset_Map, so always only one HUD (and background) is loaded. I guess that I can use z as 99999 instead of a viewport, but this also requires to bind the create/disponse methods in the correct entrypoints.