Dragon Ball x Sonic crossover au where, instead of Sonic characters just being in the Dragon Ball world, Sonic characters go through both the normal Sonic story arcs and the Dragon Ball sagas.
So one year they are fighting against the metal virus and the next year Sonic is on his death bed with the heart virus.
They go to Namek one month and when they get back to Earth they have to stop the Eggman empire from taking over the world.
Both the chaos emeralds and the dragon balls exist.
Sonic can use the chaos emeralds to go super, but he can go Super Saiyan of his own accord.
Going super gives him basically infinite stamina and increased strength, but it needs chaos emeralds to work. Going Super Saiyan makes him much stronger, and he can do it at will, but it is also much harder to control, makes him incredibly angry, and takes a lot of energy.
(So many ideas are floating around in my mind)
(But also some plot points are combined. For example, the Namekians are actually Echidna’s, and Sonic and Shadow are Saiyans)