I read the variants in Unearthed Arcana and in the Complete Warrior, and thought many of them could fit in nicely with BR.

From the Complete Warrior, I think that the Swashbuckler fits in nicely with Brecht and Anuirean characters, and the Hexblade might fit Elven, and maybe even Vos characters. The non-spellcaster paladin would fit in nicely with Cuiraecen paladins, and the non-spellcaster ranger with the Elves.

In Unearthed Arcana the variants are even more numerous. The Cloistered Cleric, might fit with clerics of Avani or Ruornil, the divine bard with worshippers of Laerme. There are many other options as well.