Gohan could gain better control over his emotions during training with Whis. This is important because in battle, a clear - headed fighter is more likely to succeed. Whis could teach Gohan how to stay calm under pressure, which would enhance his performance in fights. Also, Gohan may learn some unique moves that are exclusive to Whis' training regime.
The theme of isolation also pops up. Sometimes, Gohan isolates himself to train, away from his loved ones. This gives him the space and focus he needs, but also creates internal conflicts as he struggles with the loneliness that comes with such intense training.
The 'The Music Never Stopped' is based on a true story. It's about a father - son relationship. The son has a brain tumor which affects his memory. Music becomes a way to reconnect them as certain songs hold memories for both. For example, the son's love for music from his past helps bridge the gap between his damaged state and his family.
The fanfic might show that Broly, despite his usually aggressive nature, has a soft spot for Gohan's potential. He could see Gohan as a worthy successor to the Saiyan power. So, he trains Gohan with a kind of rough love. During the training, Gohan might struggle at first with Broly's intense regime. But as time passes, he starts to adapt and even surprises Broly with his growth. They could form an unlikely bond through this training process, which could be a central theme of the fanfic.
One possible plot could be that Naruto and Gohan start training together. Naruto is amazed by Gohan's Saiyan power and Gohan is intrigued by Naruto's ninja skills. They exchange techniques, like Naruto showing Gohan how to use shadow clones for training efficiency and Gohan teaching Naruto how to sense and control his ki. Eventually, they team up to face a common enemy that threatens both their worlds.