That tread had some interesting reading.
To bring some Conan RPG perspective though. Conan RPG specifically doesn't has such things as good or evil- not because it is mostly gray, but because back then people still hadn't thought in terms of good and evil. More so, many cultures are affected by nonhuman races which lived in their lands before them- and many races have at least some traces of nonhuman blood in them. And unlike in Shadowrun, it doesn't means elfs of dragons- it means serpentmen which had build an empire before first dinosaur was born, or demons from between worlds.
In Shadowrun, spirits are, in a way, secondary to metahuman races, most being originally summoned/created by metahuman mages. Even most Toxic spirit represents metahuman or nature corruption. Horrors might be all evil as far as metahumans are concerned, feed on fear and pain, and corrupt all that they touch, but they still are forces that can be understood using metahuman terms.
In Conan RPG demons are Lovecraftian beings, which existed for millions of years before first ape that would eventually develop into man made it first step. A lot of them might appear understandable using human terms, unlike Horrors they don't actually feed on human fear or pain- even if they usually enjoy torturing humans for entertainment, and it is much easier to make a mutually beneficial pacts with them, then trying to do anything similar with Horrors. However, when you look deep down into them, they are much more alien to mortals then even Horrors- and while appearing evil, they are not- simply because calling them evil is applying human term to something which, while might be reasoned with by humans, is in no way human.
And sorcery in Conan RPG is similar- sorcerer learns secrets of powers that existed millions of years before first human was born, makes pacts with beings from Outer Darkness between stars, and ultimately, from the very first moment when he actually can be called a sorcerer, isn't fully human anymore. To quote the main manual, "The very process of becoming a sorcerer wreaks permanent changes to the very soul of the arcanist, changes that other sorcerers and supernatural entities can detect just by looking at him."
Which is the approach to magic which I want to replicate with this character.
Speaking in power terms, yes PC's abilities will need to be balanced. There are enough ways to do that though- advanced blood metamagic techniques aren't that easy to find source to be studied from, shadow spirits sane enough to make workable pacts with aren't that common, PC's chosen style of magic might attract some attention that he would really rather avoid, some of shadow spirit abilities might not fully work for PC, ets ets.
Also, how would this specific setup work for a starting PC- compared to a more traditional starting mage builds.