I actually think the sex scenes in Sora's arc are well played with the story(Without biasness to Sora)
. It gives us more emotions and feeling of incest is very much "fleshed out".
The ecchi scenes in other arcs are the ones that are unnecessary I think.
. Though in Nao arc, the NTR feeling was delivered to Sora in those key ecchi scenes. So I can say that the ecchi scenes were a liability or an asset depending on the scenes.
@
Ascaloth not going to argue with your post since I see your point. But I advice you to stay away with omnibus format animes.
like Amagami, Amagami, and Amagami.