Naruto's character would become more versatile. With the Gum - Gum Fruit powers, he'd be less reliant on just his chakra - based techniques. This could make him more confident in different situations. He might start to see battles from a different perspective, one that combines his ninja skills with his new stretchy powers. His carefree nature could be enhanced as he has fun exploring his new abilities.
If Naruto ate the Gum - Gum Fruit in fanfiction, his character development would take an exciting turn. He'd have to adapt to having a body that behaves very differently. This could lead to him becoming more resourceful. He'd also have to learn how to control his new powers, which would require patience. As he masters the Gum - Gum Fruit powers, he could become a more well - rounded fighter, and his reputation among the ninja world would grow as people are in awe of his unique combination of powers.