That would have been such a cool RP option to have in the game!
But indeed it looks like there are no downsides for Tav, I guess Astarion's blood is OP like that. Tav can probably enjoy all the benefits of being a living vampire as he does (as long they stay near him), just doesn't gain new abilities like summoning creatures, and so on.
The Ravenloft style vampire bride / groom theory suggests Tav doesn’t actually need Astarion for those benefits, and Astarion is actually just gaslighting them so they still believe they are trapped. In actuality, they might not be under compulsion at all, nor need to stay close to him. In fact, if that theory is correct, the only binding part of their arrangement would be that if either of them harms or kills the other, they both die.
If the cravings came up in a scene though, DUrge should probably have full control over it since they’re use to dealing with the urge.
