A youtuber named Swaggy Thunder made a video that is very interesting to me and that is Time Travel power from Garnet and Steven's Fusions.
https://m.youtube.com/watch?v=jE2xfzl4GE4
He say that a person that he can't remember made a theory about the possibility of Garnet and Steven's Fusion gain a Time Travel power combined of Garnet's Future Vision and Steven's Dream Power
Think like this..... When Garnet and Steven fuse, They use a Time Travel power to go to alternate timeline but Garnet doesn't experience this but Steven does experience this since he have a Dream power. He's basically can go anyone's dream even Gems!
If they does fused, Steven will probably get more answers by going to different timeline like what if Rose didn't give birth to Steven or if Homeworld succeed of taking over the earth
I think it was be a callback to Winter Forecast where Steven get a future vision from Garnet temporarily in order to see the possible outcome of the event.
I see one of comment by Ethereal - Twenty and this is her comment
"I think one of Rainbow Quartz's power would be telekineses (Pearl's sand/cloud controlling powers + Steven's floating power)"
I don't know what was Smoky Quartz's power was but those two concept sound pretty interesting and hopefully we would get those Fusions at some point.