Disclaimer: I do not own Dragon Ball, or any of its associated characters and lore. That right belongs to Akira Toriyama.
The Pragmatic Approach to Planet Brokering
Gohan's House, East District, Mount Paozu, Planet Earth, Age 749, September 1
For many years, the elderly Human martial artist, Gohan, had lived solitarily in one of the most secluded places on Earth to better develop his strengths and connection with nature until the day a blue-haired teenager from West City came to his home on something of a quest. Not one to turn away a young traveler, Gohan welcomed the girl, Bulma, and showed her one of his traveling mementos, which she described as none other than a Dragon Ball.
"Amazing." He commented to Bulma once she finished explaining how she found a Dragon Ball in her family's possession and used a self-made gadget to track another before coming to Mount Paozu. Gohan had heard of the old legend long ago and was admittedly intrigued when he first found his keepsake which had a resemblance to a similar object owned by his one-time Master Roshi, but he didn't know what the Dragon Balls actually looked like until now. He had to give Bulma credit for her knowledge and adventurous spirit, but there was one thing he was curious about. "May I ask what you want to wish for when you summon the Eternal Dragon?"
Bulma's expression turned downcast, but she eventually answered. "To save the world."
"Huh?" Gohan couldn't help but wonder what she meant by that before his eyes widened and his expression became serious when he guessed what distressed her. "You're talking about the Great Ape monster."
"Yeah." Bulma sighed. "Glad to know someone, even in a remote place like this, knows about it, though."
Gohan shook his head solemnly. "I was here around the time that beast destroyed East City, after all."
Bulma frowned heavily at the mention, having been a small child when it happened. What Gohan didn't know, however, was that Bulma had a good idea what the Great Ape really was: a Saiyan that was slowly, but surely reducing Earth's population to sell the planet to the highest bidder on the galactic black market. While she would've liked it if her one-time alien police officer friend had been able to help when the Great Ape first started appearing, Jaco was convinced that the Saiyan race's employers had already seized Earth as their own and were simply taking their time destroying Earthling civilization out of either training, sadism, or both, and, as much as he hated to abandon his Earthbound friends, he had no choice, but to leave the fighting to Earth's people. Pushing those thoughts, Bulma forced a confident smile as she then told Gohan. "Hopefully, though, with the Dragon Balls, I can wish that monster and every other creature that threatens our planet to be gone for good."
King Castle, Central City
At the home of King Furry, Monarch of the Earth, he begrudgingly welcomed a needed, but not necessarily wanted, asset to quell the Great Ape menace that had plagued the world for twelve years and counting.
"I'm pleased that you accepted my invitation to come here, and discreetly no less." The Canine Earthling sternly said to his guest in the martial artist attire, who Furry himself would've gladly arrested if he had the manpower to do so.
The man on the opposite side of Furry's desk merely smirked arrogantly in the face of the King's concealed hostility as he replied with a mock bow. "Come now, Your Majesty, Mercenary Tao is at your service in this matter." Chuckling, he added. "So long as my ten billion Zeni payment is waiting for me."
Furry had to restrain a growl at the assassin's selfishness in the face of world destruction, but instead showed a briefcase holding the money in question. "Kill the Great Ape, Tao, and it's all yours."
Smirking widely, Tao bowed a bit more gratefully as he replied. "I'll gladly do it, Sire. That abomination has been showing me up as the world's strongest for quite a long time. I just didn't want to kill it for free exactly."
The Guardian Lookout
On the ancient platform in Earth's geostationary orbit, Kami, the offworlder who served as the planet's Guardian, had been observing events on the surface below for quite some time. Seeing the Guardian's grave expression, Mr. Popo, Kami's lifelong assistant and friend from the Other World, said to him. "It looks like things are at a standstill for Humanity and the other beings that we share Earth with, Kami. What do you think should be done?"
Kami sighed in dismay, but ultimately replied. "I don't know, old friend. When I learned how young and alone our invader truly was, I wanted to give him the benefit of the doubt, but my lack of direct interference has led to the boy bringing the Earth to its eventual destruction. I never thought I'd say this, but we must have faith that the Dragon Balls in the right hands can wish away Kakarot's evil before even graver threats make their move."
Cooler's Spaceship orbiting Earth
Onboard the circular spacecraft quite common for the ruling elites of the Planet Trade Organization, Frieza and Cooler Forces alike, the tyrant, Cooler, observed multiple media and military reports of the havoc Kakarot, Cooler's Saiyan of interest for the last twelve years, had recently caused on Earth when Cooler had made his yearly observation of the situation. Next to him, Salza, one of Cooler's top three subordinates stood in attention as his Lord and Master looked at the Earthlings' reactions with amusement.
One report actually brought a cold smirk on Cooler's face. "It appears that Earth's highest authority has secretly hired his planet's greatest assassin to kill the "Great Ape menace", Salza. Any chance that will actually work in their favor?"
Salza laughed cruelly at the question. "Unfortunately for the Earth whelps, Lord Cooler, I firmly believe that will only make the monkey even madder and hungrier for revenge. Every respectable Planet Broker knows that your enemies should think thrice before making things personal on the Broker's end of things."
Cooler chuckled at Salza's words. "Indeed, Salza. Still, I hope that Kakarot continues his tactic successfully and won't be blinded by mere rage. Good Saiyan strategists are hard to find, after all, given their extermination in the last decade."
Remembering the destruction of Planet Vegeta quite well, Cooler had sent a probe to follow Kakarot's Attack Ball to Earth out of curiosity on whether or not the genetically grown up son of Bardock would be able to rise up against any challenge, and was presently surprised to see Kakarot slowly conquering the planet in light of the few beings who could've challenged him in his youth as well as the potential uses Earth's people and technology had. In the end, Earth as well as Kakarot would be prizes for the Cooler Force to gain, not Cooler's immature brother.
Brown Country, Diablo Desert, Mount Paozu, Earth
In the local saloon of the cowboy-themed town, a pair of hardened rogues in their late teens enjoyed themselves with drinks as the other patrons looked at them in fright. The female of the pair was a green-eyed blonde with a red ribbon in her hair and a gun holstered to her hip while her male counterpart was muscular with spiky black hair and a brown tail that he covered around his waist as if it were a belt. While the spiky-haired young man was a new, yet intimidating, mystery to everyone in the saloon, many of the patrons recognized the blonde as Launch, the infamous robber with a bounty of two million Zeni, but after the first guy broke a prospective bounty hunter's arm, no one else was brave enough to go against them.
Looking around the saloon at the shaking fools surrounding them, Launch's partner in crime snorted in derision as he told her. "Talk about a bunch of weak cowards, huh, Launch?"
Actually giggling, Launch kissed her strongman on the lips quickly before then saying. "No need to bother with the vermin, Kakarot baby. They're all beneath us, no matter what."
Had a thought on the Dragon Ball SpaceBattles thread of what Goku/Kakarot could've done if he was on, or thought he was on, a Planet Broker assignment on Earth, and, considering that some Earthlings would've overpowered and/or outsmarted him even in his Great Ape form, especially if a Galactic Patroller can be called upon for help in such a situation, that he would use the art of patience to slowly make himself stronger in his regular form while staging systematic Great Ape attacks all over the planet to prepare for the final battle to conquer Earth, with a submissive population of survivors to boot. The Frieza/Cooler/Cold Force does subjugate some useful species, after all.
I admittedly wanted to portray three AUs in total that have Kakarot conquer Earth in either Frieza's name if he was kept around, Cooler's if the elder brother intervened in his spaceflight, and/or Cold's if the "Good King" didn't retire, but I decided to just stick with what I depicted in this for the sake of argument. I also genetically enhanced Kakarot's physical age to make him doable to prospective girlfriends around Bulma and Launch's age range, and paired him up with the latter because I figured it would fit with the blonde personality's aggressive, opportunistic mindset, but I'm sure the kinder, blue-haired personality would still have a soft spot for Kakarot as well.