Personally, I don't think you need more from 8. You've already got:
Squall
Selphie
Seifer
Fujin
Raijin
I suppose Laguna would be an interesting character to add,

Zell. You NEED Zell to fight Seifer! While I don't think you neeed more from VIII, I'm leaning towards you, buddy. We need Zell.