I'm about midway through the dawnguard story and chose to become vampire lord, I learnt about the woman in theives guild who will change your face but wont do it to vampires and demands you revert back before she'll do anything.

My question: can I revert back, change my face, then regain vampire lord status without losing any perks or progress in any way? thanks

Might be easier to just pick another character to go with the face changing part as I bet that the perk/progression will probably be lost.

Yes, I did that exact same thing. Just talk to Serena when you're done changing your face.