Might as well cover the villains now.
Piccolo Daimao - It would be fully explored how his experience of seeing humanity's darker aspects influenced the mindset of Daimao and the corruption of his original self, rather than have it be an off-hand statement from Kaio. Daimao would therefore be somewhat justified in using his reign as an experiment of humanity to test it's true nature and the climactic battle would be to him less a supervillain fighting a vengeful hero and moreso him attempting to prove humanity's worth, or lack thereof. However, Goku's disinterest in such moral complexities would force Daimao into acting as he did and see Goku as an example of what he was trying to prove and fight against, thereby making Piccolo's vendetta against him all the more poignant.
Freeza - His views of his father and his upbringing would be far more central, with it being fully explored that his pampered upbringing was the primary influence of his superiority complex, with his outbursts upon being surpassed being both due to what he was taught about being a superior being and outrage at the fact it seemed Cold lied to him. I'd also make some more of his family canon such as Coola or Kuriza, though not playing the roles they did in their own stories, as a means of offering more interactions and layers to Freeza's character.
Cell - As I've said many times, Cell had the potential to be the most complex and interesting main villain, but had the execution to make him the worst. Here, I'd have him live to his full potential by having the traits of Goku, Piccolo, Vegeta and Freeza constantly clashing against each other and affecting his internal logic. Like Saiyan Arc Piccolo, he'd begin to question his true objective and existential goals during his time alone waiting for the Cell Games and each match would influence his personality. The Goku within him would have him be made excited by his match with the original before the Vegeta and Freeza within him cause his superiority complex to become apparent. Gohan may also pity Cell as a being forced by his very nature to play a role that Gero puppeteered, offering an additional reason as to why he didn't get angry against Cell immediately. After SS2 Gohan stomps him, Cell's self destruction would be less about complete desperation and more to him wanting to prove Gero's perfect creation could overcome any obstacle. Once becoming Super Perfect Cell, he'd at first seem resolute on having an honourable battle with Gohan before his Vegeta/Freeza influence forces him to sneakily attack the fighters with a Shunkan Ido + Death Beam combo, resulting in Trunks' death. Things go the same from thereon, though it'd be established that Gohan had mixed feelings about killing Cell. He'd pity that Cell was forced to do this by his genetic makeup, but acknowledge there was no other way than to destroy him.
Boo - The split between his Good and Evil sides made his internal conflict external and childishly simplistic, as well as a ripoff of Kami and Piccolo. Instead, whilst I'd still have Evil Boo exist, it would instead be through Fat Boo adapting his body to fighting as a progression of him quickly learning techniques, with the gunman's actions being an influence on his change in character and not just a plot device. As such, he'd be far more merciful towards Satan and Videl, not killing the latter. Due to not being as smart as Evil Boo, his absorption of Gotenks and Piccolo would be presented more as a quickly improvised gamble rather than a thought out strategy. As such, Pure Boo is far more justified in his existence as Pure Evil Boo isn't a thing once Vegeta removes Fat Boo from his Pod, wherein it's established the Kaioshin weren't absorbed by Boo, but influenced his way of thinking to the point that he separated his personality into two groups of Fat and Pure; no longer simply good and evil, but of thought and instinct, nurture and nature.