Would you like to play as a Necromancer with the ability to upgrade Vampires?

Whatever you say, if you allow upgrading vampires, then also allowing butterflies from the Griffin Conservatory... another question is how to do it so they aren't imbalanced, but the fact is that unupgraded ones are completely worthless.
... maybe ban attacking neutrals with vampires alone?
In general, if you exclude fights where vampires and Wights slaughter crowds of pedestrians, as well as corner-cheese in the Griffin Conservatory, it would be fine, but isn't that too tedious?