The angelic doctor, Thomas, touches on something important with his
beati in regno coelestia videnbunt poenas domnatorum, ut beatitudo illis magis complaceat, [The blessed in the kingdom of heaven will see the punishments of the damned, in order that their bliss be more delightful to them, STIII Suppl Q94, Art1, tr. Clark and Swensen; i.e it's quite literal]
which I first came across in Nietzsche's Geneology. There is something, well, barbaric about this strain of "hallowed" Christian tradition, a strain quite alive today.
But then what's an exclusivist to say? Does the end of the damned torment the saved--the lost brother, mother, sister, father, spouse, friend? That wouldn't be much of a salvation. Nor would it seem fitting for them to be neutral about it, shrugging their shoulders as it were with a heavenly "Oh well." Sure, CS Lewis (The Great Divorce) might say that the damned should not have the power to torment the saved--but that's a dodge; the question is not one of the damned actively causing sorrow in the saved. Even if the pain and sorrow were, say, merely supererogatory, still it would be a surprise to hear all of the saved always feel neither pain nor joy at the fate of the damned.
Then what? Maybe God "damns the memories" of the lost, so that memories of them are wiped clean from the saved. Is that metaphysically possible though? That is, one could make a strong case that the Augustinean "inner man" would not survive such a mutilation intact, at least in some cases, e.g. where a parent or child or spouse is damned.
And if it were possible, would that be the kind of act God would have recourse to, even if it were permissible? That's a tough question, of course: God is free, free, free. But that is enough perhaps for a seed of doubt about exclusivism, no?