Sofia Boutella as Lucia for DMC6!
Are we talking realistically or dream choices? Because I'm pretty sure Capcom is only willing to give enough for casting to hire around the power ranger budget and I'm pretty sure Sofia Boutella is out of said budget. Why do you think they didn't have a Kyrie. Only enough for the cast they had.
I don't subscribe to that whole 'only people of the same race and nationality can represent themselves.' Antonio Banderas makes a fantastic Mexican. As long as the model fits the bill I say she can be from anywhere. I'd rather have a French VO, though, so she can nail the authenticity of the French accent. If she's not but can pull it off I'd be fine with that, too, but I'd rather get the authentic thing since you can often hear the minute differences and that really throws a wrench on the experience for me.
I've thought about this on occasion and there none that really fit the bill. For example, there is this one woman called Jasmine Tookes. Lucia is more brown than black but she has the features. The issue is that she only looks the part at certain angles: