You can tell when a class/race combination has been added in as an afterthought, and when it's been thought through. Tauren Paladins come to mind (look it up if you don't know what I'm talking about) as a decent and interesting lore reason why Taurens can be Paladins. I don't think Carbine would add them in as an afterthought, but I think they've thought about it. They're not just going to plop them in and make them look and feel like <REDACTED>. They want people to love the game as much as they do, this doesn't mean bending to the will of others. It means that they make a rich lore with interesting and fun gameplay and entertaining environments, if Mechari fit lore-wise, it would make the spellslinger more steam-punk driven, if not, that's fine too. Either way Spellslinger is an interesting idea lore wise, and will have really fun gameplay.