Outline using overlapped sprites is really inefficient. Shadows - maybe, as a separate sample. I really try very hard to avoid adding features which are easily "abused" - those two mentioned earlier are really easy to abuse, using it for a score counter or timer which changes every frame is incredibly inefficient and will cause huge stalls.
Having said that though, there is a way to do shadows far more efficiently than having a black tinted duplicate, but I haven't had the time to implement it. I'll have some time to re-evaluate priorities after 1.90