Like the Red Queen up there, I typically don't start working on "themed" playthroughs until at least one full run is finished, so I have an idea of what themes might work and how they are (or are not) addressed in the game. Then I'll bundle character creation and backstory and choice of love interest around that theme. There are interesting possibilities regarding Astarion, the tadpole, the lure/cost of power, and what is justified in the name of survival, but I'm not sure how.... influenceable Astarion will be, whether there's any chance of swaying his beliefs or the path he's walking. There's also potential with Gale if we get more chances to call him out on his crap.
First run is just going to be me grabbing Halsin, Minsc and Jaheira and having a grand old time exploring a strange new world.