As long as the mustache makes the transition to LEGO, you’re fine.
To be fair, though, a Bill “The Butcher” cameo probably would have worked out, that’s a pretty iconic look.
In addition, he tells Entertainment Weekly that when you’re transforming all of these characters into LEGO minifigs, it can be difficult to create a look that’s able to express everything you need to express in just a look.
As cool as it would have been to see Moriarty make an appearance, that character, being born of literature, doesn’t really a visual representation who would be universally recognized.