So, I just found this video that shows what could happen to Tav who tried to toy with ascended Astarion and dump him after becoming his spawn, pretty much being the worst case scenario of what I suggested in point 23 in the OP. That would have been one dark and angsty ending, that's for sure. Fitting actually, there should be dire consequences for messing with a possessive vampire lord.
That was a cool video. Definitely love the vampire lord energy that it was giving off.
