I have a hard time wrapping my head around the new "Paths" element to magic in 5e, of which Blood magic now is. (Still a twisted form of magic, not recommended for players)
My biggest issue here, is like many others have said, Spirits are already powerful, and magic is already powerful. And this, no matter how you want to phrase it, or "karma it away", still upsets a balance that is built into the magic system . (the limitation of Spirits per tradition). Unlike deckers, you ultimately get capped on what they can do by their gear (or Riggers for that matter), Or Street Sams by their Essence, there is no such cap for magic.
In theory, a player could invest every single point of Karma over his career into just two things, raising his magic attribute and initiation. If that career spans 3000+ karma (as is the case in my mage) that means you are running around with a mage with a magic rating of 30+ and initiated 24+ times. However, a Cyber or Bioware character, no matter how much money he has, is still limited to his 6 essence.