The plot might involve Goku SSJ4 teaming up with some unexpected allies in the Tournament of Power. He could be using his SSJ4 powers in creative ways, like combining them with the techniques of his new allies to gain an edge over the other universes' competitors.
I think Broly could also be a really tough opponent. In his Legendary Super Saiyan form, he has incredible power and his rage - driven fighting style could give Goku SSJ4 a hard time in the Tournament of Power. Broly doesn't hold back and his raw power could potentially overpower Goku if he's not careful.
In some fanfictions, Goku Black has been depicted as having a hidden power reserve. In the Tournament of Power, he could tap into this reserve and achieve a new level of transformation. This new form would give him increased speed, strength, and energy projection. He might use this form to take on multiple strong opponents at once, like the powerful warriors from Universe 7 or other universes. His attacks could become more unpredictable, such as his energy beams changing direction mid - flight to catch his foes off - guard.
One interesting plotline could be Goku discovering a new form during the Tournament of Power in the fanfiction. This form might give him an edge over the other powerful opponents.
Vegeta can also be extremely powerful in these fanfictions. He's constantly striving to be stronger than Goku and might gain some new abilities or techniques for the tournament. Another character could be Jiren. In the original Tournament of Power, he was a very tough opponent, and in fanfiction, he might be even more powerful or have some different backstory that makes him a formidable force.
In fanfiction, Goku Black might have some unique power - ups during the Tournament of Power. He could tap into a new form that's even more menacing than his regular state. This would give him an edge over his opponents and make for some exciting battles. He might also use his wits and manipulation skills to turn the other fighters against each other.
Hit would also make for a fascinating pairing. Hit is a skilled assassin with time - manipulation abilities. He could be a great foil to Goku Black. Maybe Goku Black tries to outwit Hit in his time - stop techniques, or they could form a temporary alliance based on their mutual desire to eliminate certain opponents in the tournament. There would be a lot of cat - and - mouse action between them.
One idea could be that Goku Black forms an unexpected alliance during the Tournament of Power. Maybe he teams up with a weaker universe's fighter out of a sense of pride, thinking he can make them strong enough to be a worthy opponent. Another could be that Goku Black discovers a new form during the tournament that is unique to this alternate version of himself.
If Broly participated in the Tournament of Power, he would be an absolute powerhouse. His raw strength and uncontrollable rage could either make him a wild card that disrupts the whole tournament or a key player for his team. He might start by randomly attacking opponents without much strategy, but as the fight goes on, his natural fighting instincts could kick in and he could become a real threat to the strongest fighters in the multiverse.