The linear way to boost Vivi's power is to cast noncreature spells, but there are plenty of other ways to raise its power like Clout of the Dominus and Naru Meha, Master Wizard
In terms of special versions of cards, I dont think anythings going to top being able to get a grand for the foil Japanese alternate-art Liliana, Dreadhorde General as spotted on eBay, but I think Oko has a shot to be the new champion
One drawback would be that Oranguru does require three colorless Energy to do 70 damage, but with such an interesting and situational attack, the worth may outweigh the risks of using this card
If you already have clean artwork and know what text you want on the token, the whole process takes a few minutes
Because commanders now go to the graveyard when they die, they are eligible for selection
Eventually, I went with lots of cards that synergize with Isshin and happen to be some cards I enjoy playing