I had a very similar thought; loot containers scattered around with randomized "better loot" instead of the "end loot". Obviously, there is wiggle room for discussion.Personally, I think they could get rid of the loot room and just have that stuff scattered around the POI so that those who fully explore get everything. The true "loot room" is the quest reward when you return to the trader. Why do we need the loot room treasure AND the trader reward treasure anyway? That combo usually leads to the player getting well beyond the difficulty curve of the game anyway.
If the containers are scattered around, those spawn points CAN be easily randomized so there isn't just two or three possibilities. I know the loot rooms were originally conceived as the treasure room for a dungeon but there's really no need. The trader reward is plenty especially if there is a nice crate of goodies still present in the POI but just in a random location.
But I have to disagree with equating and linking the "loot room" treasure to a "trader quest reward". It is a major restriction with an obvious downside. Not all players do quests and they enjoy it that way. I for one prefer no loot respawn and no trader quest runs.