josoo, we're another family with two maids as well. i think you're doing great already, 150 sq. ft? my two maids are in their bunk beds in a small room on their own, not NEARLY as big a space as you guys gave them. I hired them from the Philippines and both are happy with the arrangement. It is a tight living space, but they have brand new furniture and a decent work environment. I think they know what's out there and appreciate what they have.
Of course, there are people with 4000 sq. ft homes who can afford to give their helpers completely separate QUARTER mansions to live in, but you have to know what's out there to appreciate what you have.
We went house hunting, you need to admire the 'creativity' people put into accomodating for their maids. Not only that NOT having their own rooms is the norm (our agent was quite quick in pointing out that not a lot of people ask to have separate rooms for the helpers, most just room them with the kids). We saw day beds that people pull out in the kitchen that helpers sleep in or literally closets that people fit beds into for their helpers.
When I see 8 out of 10 arrangements with helpers accomodations like that, I don't think we are seeing the extremes but rather the norm.
My daughter's room only has a tiny window, which opens up directly into the wall of the neighbors, we don't even open that window now. Does that mean i'm putting her in a prison cell? We live in HK, and we deal with the situation, just means that she's spending a lot more time playing in other rooms where there's much more natural sunlight.
How about this... if they choose to, your helper can always sleep in the living room where there are plenty of windows. I think you're being a great employer already.