I mean, more choices are always good.
That said, you spent the whole game listening to Astarion going on that spawns have no freedom at all and you want to become that? You would be totally dependent on a guy on a total power trip. Ascended Astarion is just the worst.
And for non repending Durge:
I'm pretty sure, father dearest wouldn't allow that - it should not be an option for a Durge , who stay the Chosen of Bhaal, since it is pretty clear, that Bhaal wants full control over his minions, so he can't be ok with his Chosen becoming the spawn of some upstart vampire
