Not sure I get the concept lol, Luffy is both Joyboy and Nika throughout the ages. He'll fight both enemies eventually, thats the point of the series.
The concept is that Nika is an actual deity that exists, and shows up to fight Imu
Zunesha thought Luffy was Joyboy because she or he heard the drums of liberation, but Emeth thought Joyboy was there too when he heard them, but when he met Luffy, he confirmed Luffy isn't Joyboy, Gear 5 just looks like Joyboy's transformation
[automerge]1761312657[/automerge]
This would parallel Luffy vs Kaido
The alliance on their own failed, and Luffy died, if Nika powers didn't show up, Kaido would have won
Kaido's fruit has some Satan parallels, and a panel of Gear 5 Luffy vs Kaido mirrors a painting of God defeating Leviathan
Nika has lots of Jesus parallels, and Imu has lots of Satan parallels
Just like the raid would have failed if Nika powers didn't show up, whatever will happen to fight against Imu will fail, if Nika doesn't show up
Nika powers saved the raid, and then put that on a bigger scale, Nika will save the final war