THESE ARE NOT SUGGESTIONS! These are ideas to keep in mind for the future.
Utumno: Maybe a biome around the valley where it is? Nan Udun maybe. It would add another achievement and give a hint for new players to explore there.
New Utumno Troops: Bombardiers: It seems that it would make sense for the orcs of Morgoth the have access to explosives, as Sauron did.
Chieftains: Not for troops! A rarer spawning mob that has a slightly higher chance to drop Gear and Key parts.
Chests: Rarish spawning chests! Adds even more loot!
More rooms: Just more general possible varied generation options.
(In my mind, the old Utumno before the update that made it much more ruined is the Utumno of the Spring of Arda, while the current Utumno is the older ruined version of the Third Age.)
Forodwaith: Recently it has been revealed that changes to the Forodwaith map are coming in Renewed. Could these be...
More biome variants?
More visible biome variants?
Maybe more waypoints, or a new biome surrounding the North Pole? Dor Bendor, land of the shifting frosts?