I think Scion ties in heavily with Conjuration, more than the other way around. I though of scion as more of a use of the conuration to further ambition, where conjuration in and of itself is just an arcane art, like the others. Sure, necromancy makes a sense since it reverses the progress of nature, but I can see more shades of gray in conjuration.
The typical retort I have seen is that conjurers tear open the planes and force the servitors into submission against thier own will, which makes sense, but is also a cop out. The same could be said about transmuters unnaturally contorting nature's vessels and destroyng what nature ha built, or invokers harnassing the elementals of nature and using them for thier own unnatural gain, etc. etc.
Anyway, this sounds pretty cool, and I am having more and more ideas for nice discussions on the matter in character, I might have to give it a crack....I wonder if anyone else has made a true effort of breaching the subject in game. I think that a stance of it is more important how you live the life in the natural order of things than what arcane arts you follow.