Do not underrate your customers , I think most of us would like to see more mature games. On the other hand, first priority should be to make the game good, do not yourself force into things which you call serious issues. I can imagine myself playing game for example about (at least partially) poverty (I'll take poverty as an example, but all other themes you suggested could be probably substitued in next text), but still, it has to be done well. Also, do not overrate seriousness of issues you were talking about. While game about poverty surely has a great potential (this is important, although poverty is surely mature theme, it may be hard to explore this theme adequately deeply) to be more mature than game about rescuing a kidnapped princess, theme itself is not extraordinary deep . What I want to say is that you do not necessary have to use theme like poverty to make your game deep, mature. In fact it is not such a success just to pick up mature and deep theme (since not so small portion of human population is quite aware of "deep problems of human nature" [sry, my english is bad, but I think it's understandable what I wanted to say] and/or absurdity of human existence), it is a great success to actually "explore" this theme well (both in terms of artistic and "philosophical" value).
But considering a fact, that Obsidian (or BI) games are some of those most mature I encountered so far, you are in great position to push level of seriousness in games forward. So good luck with that .