This would function similarly to how the shovel's icon changes when the player is using the Shovel Knight outfit. It would be a cool reference considering that Serenade seems to take a lot of gameplay/aesthetic inspiration from the Sword Familiar.
#Reskin Serenade to the Sword Familiar from SotN when the Alucard outfit is equipped
prisma jetty
pliant stream
That does make sense they should do that.