Gem characters are named after Gem types (additionally after Gem subtypes, identification codes or nicknames for a better differentation).

But hybrid Gems and Fusions should have a different structure of the name (based on their hybrid nature and based on real identity as Pink Diamond not as Rose Quartz):

-human component: forename and surname

-Gem component: Gem type (additionally Gem subtype).

I think these should be the official names for these Gem characters:

Steven Diamond Universe - for Steven Quartz Universe

Stevonnie Diamond Universe Maheswaran - for Stevonnie

Stegory Diamond Universe - for Steg

Smoky Quartz Universe - for Smoky Quartz

Rainbow Quartz Universe - for Rainbow Quartz 2.0

Sunstone Universe - for Sunstone

Obsidian Universe - for Obsidian (fusion of Steven Quartz Universe).