Here's your conflict for Season 6: Earth stopped being a Homeworld colony when Pink Diamond was shattered; since Pink Diamond was NOT shattered, that means that Earth is still a Homeworld colony. Once White Diamond finds out that Pink is still alive, the colonization effort will restart in earnest. Yellow and Blue might be amenable to listen to reason, but you can bet dollars to donuts White will not be so easily persuaded.

There are only two ways out, either Steven shatters himself for real, or he finds a way to change the way Homeworld society operates, move it away from exploiting organic planets. In other words he's go to do what he did with Peridot, times one trillion. Compared with that, making peace with Yellow and Blue was the easy part.

The one solution:
M U R D E R C O C K