It's not impossible, but Blood elves are visible different than Night elves, aside from actually being different races despite both being elves, while Garleans are just taller Hyurs/shorter-eared Elezen. The fact that the few allied Garleans we have can pass off as Hyurs by hiding their pearls is a pretty clear indicator that even in universe they're seen as practically the same race.

Once again, it'd be far, far easier to just add the pearl as a glamour, or even give Hyurs a graphic update, than making them a whole new race