In classic BG, doesn't Kagain just say he gives up on finding ES's son as soon as you enter that area? If so, I wouldn't say that the quest is actually 'broken', but just 'never intended to be finished' (or BioWare forgot about it or didn't have time to make a good conclusion to that quest). Again, I would consider extending the quest a tweak rather than a fix, because it does come to a conclusion, although not that satisfying for the player. Any comments?
Just my 2 cents about Kagain ... original BG has the intention of "no quest" (you're right about "never intended to be finished") so why BGT Weidu should have something to add about it?
Of course it's just my thought, but i guess this GREAT project should be used to play "BOTH games in 1 game" with the ability to be compatible with some other "important" mods,
just my 2 cents,
mm75