I have this idea that the dar hollow ritual could be adapted to use BCV or even ghouls as a power source. We know it is said Dracula failed when he created the BCV, so this adapted ritual could be a success. To make it as powerful as possible, it would require the sacrifice of the remaining BCV elders. If BCV can be affected by necromancy, I guessed they could be a fuel source, in necromancy violent deaths and older bodies work the best, so the elders are perfect.