How do homeworld characters react to fusion?
Blue diamond: When Ruby and Sapphire fused Blue Diamond was not happy, she even wanted shattering to be enforced apon Ruby
Jasper: Jasper also doensn't like fusion (i think) as she says "fusion is just a cheap tatic to make weak gems stronger"
Homeworld gems in The Answer: They had a suprised "youshouldnotbedoingthat" expression as they towered over Ruby and Saphhire after they fused.
Peridot: She doesn't mind fusion unless they are fused for no reason but she's gotten use to it.
Why homeworld is against fusion (plus why Pink Diamond might not be here) (theory)
I think that fusion is dissed upon because the diamonds don't want any other gems to fuse and over power them and try to shatter them. I think that long, long ago when Pink Diamond was still in the authority fusion was allowed and Rubys were in the ground for the right amount of time to have all the traits, untill a group of Rubys decided that they didn't want to be controlled and told what to do so they fused and shattered Pink Diamond (they had to fuse to defeat Pink Diamond because diamonds are one of the strongest materials). Then when the Ruby fusion shatterd Pink Diamond they grew tired thus splitting up to catch their breath but in that time one of the other diamonds came to see what happened she saw the shattered Pink Diamond and shatterd the group of Rubys that shattered Pink Diamond so the incident could never happen again. Then the diamonds made a rule that fusion is now forbidded and anyone who fuses will be shattered, they also took Rubys out of the ground earlier so they would be dumb (as they are in Hit the Diamond (uncalled for pun)) and not smart enough to even think about fusing or rebeling. As the law of no fusing was put in place the diamonds told their gems that fusion is pathetic and fusion is a cheap tatic to make weak gems stonger (as Jasper says). However she still allowed Rubys to fuse becasue they are dumber than before so she wouldn't have to worry about it. (with the Ruby fusing with Saphhire is different because she didn't want to fuse she just wanted to save the upperclass gem because she knew that Saphhire knew she would lose her physical form.(and may still feel guilty about bunmping into her))
Gem War
Most of the warriors in the gem war (as showed by Pearls hologram and Lapis' mirror) that there are no Rubys. I think it's like this because Yellow Diamond possibly didn't want the other Rubys to join the rebelion by being convinced by the rebelion, Garnet/ Ruby/ Saphhire to join as they are kinda dumb. So instead Yellow Dimond made Quartsz gems like Jasper (and maybe only Jaspers) to fight in the war.
Diamond Roles
Yellow Diamond: Army and Repair (as Jasper is an army solider as she says she fought in the war-always refers to Yellow Diamond when something is important, Peridot is a certifyed kindergartener and a technition- "especially my diamond, Yellow Diamon", the Rubys in Hit the Dimond- looking for Jasper which is one of Yellow Diamonds soldiers so they would probably be a part of Yellow Diamonds because they arn't part of Blue Diamond)
Blue Diamond: What's going to happen, past/future, Organising where to take over (Lapis can view whatever she has whitnessed- seen in the Background in The Answer, Saphhire can predict and see possiblites for the futer- seen in The Answer and refered to a member of Blue Diamonds court,
Pink Diamond: maybe used held gems prisoner before shattering was a thing
White Diamond; possibly ruller of all as her gem looks like it could be on her forehead and above all diamonds in the authority symbol