Spend feats, yes; give up something from your class, no, unless I'm forgetting something (entirely possible).
To an extent, yes. I suppose I'm looking for something that is fundamentally different, which warforged (just as an example) were in 3e but now are not. Since I brought up DS, I will throw out thri-kreen as another example. I've been thinking how to portray them as a race in 4e. I do not think that, if DS books get published and if thri-kreen are a playable race therein, that they will really be all that different from any other race, despite being giant bug men with bizarre anatomies. I'd be happy to be proven wrong, but what I've seen to date does not fill me with hope. The designers are approaching the issue with a very different perspective than mine.