If you are a Werewolf and want to join lord harkon can you? Or are you forced to join the Dawnguard?

How do think it will go down if you're a werewolf and you try to become a vampire lord?

If you join with Harkon, you become a Vampire Lord and are cured of Lycanthropy.

Harkon's an undeadist and horror monsterist. He doesn't want a few fleas in his castle? I'll just go back to eating bandits.

And from what I understand, if you were a werewolf at the time of becoming a vampire lord, you return to being a werewolf upon curing yourself of being a vampire lord. Could be wrong about that, though, but from my understanding so far, there are no new ways to become a werewolf again in Dawnguard, at least none that have been truly confirmed, that is. Guess we'll know for sure in the next couple of weeks.

maybe. it would be dumb if you cant

They should just have places where you can flip back and forth between vampire and werewolf