To add to this:
- Steven and Rose's colour palettes would be different. No '90s kid show would feature a male main character in pink if they wanted to sell toys, unless it was the early '90s when neon colours were still in. Even then, no way would it be his main colour.
- Rose's emblem would be red, since even a flower symbol on a boy is pushing things. Her sword would be metallic silver with red accents.
- Rose herself might be reworked to have red hair and white skin. Which would make no sense for her gemstone, but that's cartoon logic for you.
- Steven wouldn't be fat. Fat characters were purely comic relief and losers back then. He would also have more attitude, even if he weren't aged up.
- His gem placement would be moved to his sternum, so the toymakers wouldn't be sued by whoever manufactured Treasure Trolls. Also because it sticking out under his shirt would be weird if he were thin.