I think I'd rather see tags for backgrounds and possibly subclasses than subraces. A noble would likely say something different when a gate guard is being unhelpful than a soldier or criminal would. I'm pretty sure a fiend warlock has very different insights than a great old one warlock and both are potentially relevant to the plot. We already have some of this in that what god your cleric worships makes a difference in some dialogs (oddly people don't like what you say when, as a cleric of bane, you say a prayer over their dead). It wouldn't work with everything (I doubt an abjurer is noticeably different than an evoker, for example, but a draconic sorcerer may well differ from a wild magic sorcerer). In all of these cases I think the amount of work rewriting and recording dialog would be enormous and probably dwarf any benefit most people notice.
