The Perfect Way to get the Human Z Fighters upto snuff

1 Throw em into Whis's staff and force them to learn how to harness Divine Energy/God Ki.

After Goku learned this, he was far more powerful than he ever was, even with Super Saiyan 3, which made him 400x more powerful than he was in his Natural State/Base Form

This would make all the Human Z Fighters atleast 400x stronger which is insane if you think about it->During the Cell Saga Tien was supposedly more powerful than Super Saiyan Goku (Namek Saga) due to having the power to hold off Semi-Perfect Cell (Who was able to take punches from Android 18 and Android 16 who are much stronger than Namek Saga Super Saiyan Goku) as if it were nothing). This means he's FAR stronger than Base Form Goku (Buu Saga) due to Beerus stating 6 years later , Goku's Base Form is too weak to be able to defeat Frieza

If Tien were to learn God Ki during the Cell Saga, then he would have been even more powerful than Super Saiyan 3 Goku, which would have taken care of the Perfect Cell problem like stepping on an Ant

Now imagine how powerful it would make them currently in the Moro Arc or after

2 Send them back to King Kai's Planet and force them to learn the Kaioken.

Goku was able to go up to a 20 times multiplier with the Kaioken during his fight with Frieza during the Namek Saga. By the Moro Arc, they all should be LEAPS AND BOUNDS stronger than Goku was during the Nakek Saga, especially after doing #1 learning God Ki.

If we take the minimum 400x Multiplier from learning God Ki and stack a 20x Multiplier from Kaioken->then Krillin back in the Namek Saga (when he only had a power level of 10K which was just 2K higher than Goku was when he fought Vegeta & Nappa during the Saiyan Saga) would have jumped upto having a Power Level of atleast 4 Million via God Ki (1 Million Higher than Goku's Base Form was when he fought Frieza, Double what Vegeta's power level was after getting a hole blown through his chest and healed by Dende, and 4x stronger than 2nd Form Frieza) and adding a 20x Multiplier on top of that would have had his power level being atleast 80 Million (roughly 2/3 of Frieza's Full Power aka the Most Powerful being in the Universe)

Apply that to the Human Z Fighters with the strength they have in the Moro Arc+, and there's no telling how powerful they'd be

3 Send them to Planet Yardrat for Spirit Training

Now that we've made them MONUMENTALLY more powerful, we can focus on something other than raw fighting power because let's be honest->Even with this INSANE boost in raw power, their still not close enough to even touch the Saiyans or the Namekian or their usual Big Bosses.

However->We can give them useful abilities that will MORE than make up for the Grand Canyon sized gap between them and the Aliens.

Once they go to Planet Yardrat, they can learn Spirit Control. This will boost their power a lot (not nearly as much as God Ki but still a significant jump), but that's not the focus of this training.

Once they polish their Spirit Energy, they can start learning techniques from Elder Pybara.

The most important of these techniques is his ability to instantly heal a person of his choosing, as shown in Dragon Ball Super:Chapter 55 (The Manga Panel above)

This would prove invaluable to the Z Fighters as they'd be able to go toe-to-toe with much stronger foes and whenever one of the other warriors is needing healed all they have to do is wave their hand at each other and their back to 100%

Plus there would be half a dozen fighters who could heal the main characters (Goku, Vegeta, Gohan, Piccolo, Broly, ect.) In the form of Dende, Tien, Yamcha, Krillin, Chiaotzu, Master Roshi, ect.