This isn't supposed to really be an idea. These are just voices in mind for the genderbent version of Steven Universe.
WARNING: SPOILERS AHEAD
CRYSTAL GEMS
Nora Universe (Female Steven Universe): Catherine Taber.
Rose Quartz/Pink Diamond: Miles Luna.
Garnet: Syrus Lowe.
Ruby: Will Smith.
Sapphire: Phil LaMarr
Amethyst: Johnny Yong Bosch.
Pearl: Yuri Lowenthal.
Peridot: Richard Steven Horvitz.
Lapis Lazuli: Scott Weinger.
Bismuth: Dwayne Johnson.
Connor Maheswaran (Male Connie Maheswaran): Ben Platt.
Georgia Universe (Male Greg Universe): Valorie Curry.
HOMEWORLD GEMS
THE GREAT DIAMOND AUTHORITY
White Diamond: Robert Downey Jr.
Yellow Diamond: Rainn Wilson.
Blue Diamond: Andrew John Hozier-Bryne (Hozier).
MEMBERS (IN NO PARTICULAR ORDER)
Yellow/Blue/Pink Pearl: Yuri Lowenthal.
Famethysts: Johnny Yong Bosch.
White Pearl: Robert Downey Jr.
Spinel: Justin Roiland.
Jasper/Skinny Jasper/Carnelian: Michael Jones.
Holly Blue Agate: Tim Allen.
Ruby Squad: Will Smith.
Aquamarine: John Hasler.
Topaz: Gael García Bernal.
Blue/Yellow Zircon: Tom Kenny.
Nephrite/Jades: Michael Peña.
Emerald: Taylor Grodin.
Pebbles: Catherine Taber/Miles Luna.
Squaridot: Richard Steven Horvitz.
Hessonite: Christopher Plummer.
Demantoid: Nolan North.
Pyrope: Rasmus Hardiker.
Lapis Lazulis: Scott Weinger
OFF COLOURS
Laura Barriga (Female Lars Barriga): Sarah Anne Williams.
Rutile Twins: Hayden Ezzy.
Rhodonite: Steve Carell.
Padparadscha Sapphire: Phil LaMarr.
Fluorite: Michael Angelis.
FUSIONS
Opal: Akihiro Lawrance Kotabe (Akie Kotabe).
Sugilite: Tramar Lacel Dillard (Flo Rida).
Alexandrite: Peter Gene Hernadez (Bruno Mars).
NorNor (Genderswap Stevonnie): Ashley Johsnon.
Malachite: Michael Jones/Scott Weinger.
Rainbow Quartz: Vic Mignogna.
Sardonyx: Rob Rackstraw.
Smoky Quartz: Eric Edelstein.
Lemon Jade: Michael Peña.
Rainbow Quartz 2.0: Kate Winslet.
Sunstone: Lovell Stanton.
Norgia: Frankie Cosmos.
Bluebird Azurite: Eric Bana