I like your idea of having "Odd races". Here is a list of races that I think would be cool to see in a "Baldur's Gate" type game: Steam Punk mechanical constructs Demons elemental half breeds Insect-like humanoids ... Zombie Koala?
Yes. Why not have one of the odd races be a bunch of Steampunk-like Mechanical creatures, that have firearms of simple design. Or touch on the "Outlaw Star" idea of having spell stored in cartridges or shells. Allowing a non-magical class to cast spells they purchase for one time use. Firearms would be cool in a fantasy game if they are not a common weapon. Otherwise you may as well go with the shadowrun approach.