If Toei came to me for an idea, this is what it would be. This arc is called "Revenge Against the Mortals". I hope you enjoy this read. There will be some movie characters in this, if Japan doesn't care about canon then I don't either.
Prologue:
The first major clue to this arc happening is during the tournament of power, towards the end when there are only 5 fighters left: Goku, Freeza, Jiren, Toppo, and Vegeta. The time remaining before the tournament ends is 10 minutes at this point.
Everyone is fixated on the tournament. The Zenos are eagerly watching. The Grand Priest looks on the battlefield then looks around at the bleachers to see if anyone is watching him at the moment. When no one is watching, and with a sinister smile on his face, he teleports out of there and arrives in a large dark throne. The place is so dark and the throne is so large. A very tall figure is sitting on the throne. The Grand Priest arrives and immediately bows down. Suddenly, Cell, Bojack, Bibidi, Babidi, Tambourine, Dr Gero, King Cold, a plethora of Sabaimen, and other demons bow down behind the Grand Priest.
"Report" A large booming voice orders the Grand Priest.
With a sinister smirk, the Grand Priest explains that everything is going according to plan, and that everything will be coming to fruition very soon.
A green looking face appears and he strokes his nose, satisfied with the GP's answer. "Tell me, how is the tournament of power unfolding thus far"?
"Universe 9, 10, 2, and 6 have since been eliminated, But Universe 7 is winning thus far. The leader is that abomination known as Son Goku for Universe 7", the GP replied.
The figure was shaking in anger at the mention of Goku's name. About 50 meters away, a small saibaman was bowing down but sweating profusely in fear. The tall figure on the throne did a mouth blast and disintegrated the pitiful creature, frightening those around him.
"Make sure U7 wins. Our plan can never go smoothly if they don't. Goku will be crushed like the bug he is when I get my hands on him. His old rivals turned allies with side with me thanks to Babidi and his father's magic. By the way, Babidi, is the ring of the 4th dimension ready? The Figure asked.
"Yes sire", Babidi replied.
"Good. Soon the greatest invasion against the mortals in the history of all the multiverses will take place. Our army will be so vast and large we will strike fear in their hearts. And it will take place in that insignificant bug Goku's home planet just for the icing on the cake. Meeting dismissed".
The GP then teleports back to where the ToP is being held and no one notices he left.
Chapter 1
The ToP continues, with the eventual last two remaining being Goku and Jiren. After numerous episodes of fighting Goku comes out on top, but the GP had something to do with that victory after the meeting with real boss. All of the other participating universes get erased by the Zenos.
When the tournament ends, U7 is gathered together. As the Super Dragonballs are being activated, a large throne teleports into view high above U7's fighters. The ring of the fourth dimension is activated, shocking all of the angels and Beerus.
The ring of the fourth dimension can change reality and rip through timelines like its nothing. It can freeze the Zenos and place them in the deadzone, the same deadzone where Garlic Jr is being held. It gives the user ultimate power. It can control all of the angels like robots and can reverse time or fast forward it at any time. It is the most feared object in all of the multiverse.
Immediately, Zeno's guards back off and the Zenos are warped into another dimension. The U7 fighters try to attack the throne and the very dark tall figure sitting on the throne, but this incredibly powerful gravitational force isn't letting them fly up, and Goku is too exhausted to use his Ultra Instinct form.
The throne levitates down to where the U7 fighters, the Supreme Kai, Old Kai, and Beerus are. Whis is nowhere to be seen and Beerus is confused. All of the angels and the GP stand next to the throne in unison.
The figure finally stands and reveals himself to everyone on the other side for the first time.
"We meet again".
Goku is in absolute shock.
Zamasu continues "After surviving Zeno's brutal attack, I found out a way to get my hands on the ring of the fourth dimension which was placed deep within the valleys of hell millions of years ago. Putting it in a universe where I reside was the worst mistake anyone could have made".
He continues "Letting you off the hook now Son Goku would be too easy. With the Zenos out of the way and the angels at my disposal, I'm virtually unstoppable. And that's not all"...
"Soon I'll have the ring of the fourth dimension completely under my control. When I control it I will have absolute power over all of the gods and angels.
Vegeta then turned blue form and attacked, but to no avail. He froze where he was and turned back to base as he fell. Android 17 just stood there arms crossed not giving a fuck about any of what's going on.
"Now", Zamasu Continued, "My army which consists of villains you fought in the past, all of the demons from the demon realm, will all invade Earth. Killing you slowly Son Goku is what I want. Killing you now would be too easy and would be letting you off the hook, and one more thing"…
Future Trunks and Mai's dead bodies are thrown to the floor out of the blue. Zamasu held the ring of the fourth dimension and smiled, "I can go to any timeline at anytime I want. He won't be a problem anymore".
Gohan is enraged but before he can do anything the entire army vanishes along with the Super Dragonballs, leaving our heroes in a big situation. (Please note even though the angels are under Zamasu's command they will not fight on his behalf since the ring of the fourth dimension will not allow them to impulse on violent commands but run errands for him and give him knowledge. They will act as spies. The GP will fight though).
With our heroes back on Earth, Goten and Trunks demand to know how the tournament went, as they are still upset they weren't invited, and even more pissed when they find out that 2 Saiyans (Caulifla and Kale) were allowed to fuse.
It is agreed upon that everyone will have a meeting at the Lookout tomorrow afternoon, giving everyone time to rest after a grueling 48 mins of fighting in the ToP. But Goku sadly admits, "Guys, although we've overcome the odds before, I really don't know if we can pull it off".
The next day in the afternoon everyone meets at the lookout. Vegeta plans to use the time chamber on multiple occasions to train, but for whatever reason the others feel like it's not going to be an amazing asset.
Freeza reluctantly agrees to join Earth's forces against this invasion. People don't trust him and believes he is only after his own agenda of course, but Goku promises to keep an eye on him.
Beerus is the only God of Destruction left alive. He is with the crew at the lookout during the meeting. He is shocked and dismayed that his mentor and friend, Whis, is gone. Then he remembered his brother Champa and grew even more depressed.
"We have to gather every single fighter you know Goku. Any fighter on this planet. Even the ones that have military experience against invasions, they might be able to give us good knowledge with fighter formations", Beerus said.
"I have a couple old enemies in mind. It's a chance for them to redeem themselves, one of them can be a soldier and the other can be a strategist to help our cause due his many years experience of warfare and combat" Master Roshi spoke up.
"IT BETTER NOT BE WHO I THINK IT IS" Tenshinhan stated loudly, veins popping out of his forehead.
Goku contacted King Kai and asked him to eavesdrop on conversations going on in the demon realm, so they know when the invasion will strike.
If an army was coming, it was imperative that they had their own army ready to defend the Earth. Goku agreed "We need to organize our fighters based on what we believe they can do for us. We have to be prepared, unlike the other times we had big battles, if we aren't ready for this one, we won't win". Goku then looked at Piccolo and Roshi, "Both of you are strategists, so I'm counting on you guys to use your critical thinking skills. We're going to need you".
Vegeta scoffed "Kakarot you can't be serious. Putting in charge the old man and the Namek? Give me a break". Vegeta was absolutely enraged that his son Trunks from another timeline was dead. He remembered his outburst against Cell. His fists were shaking uncontrollably in fury, and he was in a foul mood. He wanted the invasion to begin and he can start his revenge.
"We can't let our emotions get the best of us Vegeta. I do have a plan on what our plan of attack will be, but I need some more time to think it through. But Goku, Gohan and I in the meantime will try our best to recruit as many fighters from the past that we encountered. Heck, get Krillin to join. He's been around since you were a boy"the tall Namekian said, his white cape blowing in the wind.
"Sounds good to me", Goku replied.
"Let's summon Shenron to see if he can wish back those universes that Zeno erased", Krillin said.
Shenron was summoned but it is outside of his power to bring back all of the universes. However, if Parunga is also summoned they can combine their power to bring back just one universe. The Namekians on Namek were contacted to summon Parunga. Hence they had to make a difficult decision. The Pride Troopers would make great allies, but Goku and the gang weren't very familiar with them. Universe 6's warriors are fighters they are most familiar with, but Universe 11 is more powerful due to Jiren. Who would they choose? The decision would be a difficult one at best.
Thanks for reading the prologue and the first chapter. I'll continue the story if people want me to. Thanks for reading.