The playable races should depend on the story. Some races may not make sense then. I don't know how an Imp would fit into it for example.
Theoretically, there's always the potential to use Origins as a way to enable some different races.
It would take a lot of work, basically making a new storyline for each race (At least initially, there might be a converging mid-point where all storylines merge).
But you could technically, create Origin characters that are customizable, but locked to a specific race. Thus they can enter the story in a way that makes sense. Having like a unique Prologue and Act 1 that sets them up.
Not too unlike Dragon Age: Origins prologues, which were unique based on race (Dwarves had their own pair of prologues) and class (Mages had their own prologue)
The more work put into such Origins and thus how much they diverge from the Blank Slate start will determine how unique the race will feel in the story.
Of course, the caveat is that you might upset Blank Slate enjoyers that want to play a certain race and headcanon something completely antithetical to the actual story, universe and overall lore...
But honestly, having a unique Origin story for many (If not all) races would be ideal, in order to provide more depth to characters. But I'm apparently strange in my like of characters that have ties to the world given Larian's constant use of the Blankest of Blank Slates for their games (With even their "Origin" characters going through the most generic possible starts because they all need to end up in your party 0.2 femtoseconds after the game begins)
