I really like the notion of folding ToB into BG2 and tying it to the return of Bhaal. Even after noreloading the trilogy a few times I find ToB to be a real slog storywise, and high level gameplay is not especially interesting. Giving more options for the player is always good, for example some of the alternative content could be used to give an alternative route to the Sahuagin City if the player goes through the portal instead.