Honestly, I think Olivo has a tendency to force her voice, and wouldn't sound that great on Another Hundred People.
I do think it's a great idea for Marta to be played by a woman of color, though. In so many words, she asks Robert if he knows any people of color (it's clear he doesn't). Since he has such a homogeneous, insular group of friends, I think it works for Marta to be a woman or color.
When I see the phrase "the ____ estate", I imagine a vast mansion in the country full of monocled men and high-collared women receiving letters about productions across the country and doing spit-takes at whatever they contain.
-Kad