Yeah, the sentence could be phrased in different ways.
For instance -まで is "until", "as far as", the physical, psychological, or temporal reaching point. Here means the consequences go right after Miyuki (the end/reaching point) by sealing his "Sight".
I have seen it translated as "because of [something], [something else]-" too, in the videogame translation database that some companies use nowadays.
I didn't use "as well", "too", or "also" because the confusion in English, that is not much a problem in Japanese. A very, very long way to put it is : "If you do that, because of me, you will be incapable of use your magic". The context helps a little bit as Seit said.
oh, right totally forgot it...
BTW, is there any example of BS magicians (Born-Specialized Magician) giving birth to real magicians (Generic omnipotent Magician), because I wonder what kind of child might be if Tatsuya would ever have babies
Wasn't Miya a BS magician?
They are by definition people with unique magic abilities, right? I don't remember if it is a requirement to be unable to wield other magics in an efficient way too.