Woo, blast from the past!
I gotta say that for me DavidW's Wheels of Prophecy mod went a long way in making ToB more fun and reactive; breaks up the linearity by letting you pick your targets, and the others change depending on the order you do it. Aside from that? Pretty much the thing Beamdog did back when they were actually, y'know, doing things: character quests. Like, it's incredibly cool that Sarevok's back, maybe give him something to do? At the very least for characters like Viconia or Aerie who don't really have storylines in SoA. Just my $0.02, adjusted for inflation