-Keep the human characters (and Piccolo) competitive with the Saiyans and relevant to the plot (this is a big one).
-Probably leave Goku dead after the Cell Saga
-Probably wouldn't have bothered creating Goten, the only point of his character was to fuse with Trunks (and fusions were lame IMO)
Bonus: I'd actually stick to the Dragonball rules that they always found a way to circumvent. Meaning that the "you can only be brought back to life once" actually means once and that's it. IMO, the biggest problem with DBZ is that they made death way too cheap. It was hard to care when anybody died (regardless of how dramatic Toriyama tried to make it) when you know they'll just be revived at the end of the arc.
-Yamcha, Tien, Chaotzu, and Piccolo die at the end of Saiyan Saga - "eh, they'll just be revived" (and they are)
-Vegeta and Dende and all the Namekians are killed by Frieza "eh, they'll all get revived" (they do)
-Frieza kills Krillin "That was grimey. But he's just gonna get revived..." (he does)
-Androids 17 and 18 literally get eaten by Cell "Eh, they'll probably get brought back someow" (they are)
-Cell kills Future Trunks "They're just gonna revive him at the end of the arc" (they do)
-Vegeta sacrifices himself to kill Buu "Eh, he'll be back sooner or later" (he is)
-Buu kills...everybody, eventually, aside from Goku, Mr. Satan, and Dende - "Oh, they're definitely all getting revived" (they do)
Hell, in the Cell Saga Goku had to go out of his way to stay dead and he still got brought back eventually. It was just hard to care when anybody got killed in DBZ when they always come back (unless they're villains). You know death is cheap when Piccolo tells Buu to kill the other 6 billion people on earth just to buy a couple minutes of time (knowing they can be wished back).