Totally support this great suggestion! <3
Astarion's death shroud would be nearby but he would be completely enveloped around his love that finally helped him find safety.
The narrator's voice might at this point say something like:
“He mumbles something in his sleep, his face scrunching up slightly, and hugs you tighter as if instinctively seeking your comfort. It's clear that even in his sleep, he feels safest when in your embrace. After a few moments, his expression relaxes again, and he sighs softly, sinking back into a deeper, more peaceful sleep.” (the text isn't mine, it was given to me by a chatbot, but I think something like this would fit Astarion as a description of the scene you suggested).
Similar comments by the narrator could be added to all companions during a long rest, depending on their character.
