I am right. Just wait and see. 
But you still didn´t answer my question. Would all these factions let the world to be destroyed just because the only one person who can close veil tears uses blood magic? I would say no.
Special snowflake guarantees that.
You may very well be right but it's not necessarily your conclusion that I'm debating against but your evidence for it. You've provided nothing but assumptions and inaccurate information to try and prove what you are saying.
You have a conconclusion and you're trying to prove it with wild assumptions with no bases. I'm sure once you play the game, even if there is a way to destroy the Chantry you'll still complain that BioWare were somehow forcing you not too, because you're convinced you're right so you're not even considering other possibilities.
I thought I had answered your question when I said the below:
You don't start out as the Inquisitor, you start out as some guy who becomes the Inquisitor, even if you did start out as the 'mighty' Inquisitor, why would factions who don't like Blood Magic work with you - there would have to be a lore breaking story reason for Templars, Mages, Dalish, etc to work with some who uses Blood Magic, so you'd end up with no allies, except possible the Dwarves because even the rebelling Mages don't like Blood Magic
But let me elaborate further.
At the beginning of the game you are just some guy, some guy that has to gain Cassandra's trust so she doesn't kill you right there, if you are a Blood Mage at the beginning of the game - then you're dead.
If you become a Blood Mage later in the game, then either one of two things has to happen - everyone has to ignore the fact that your are a Blood Mage like in DA:O and DA2 or they have to react to it.
Since BioWare is trying to lessen the disconnect between the lore and the gameplay by making people react to your class, then they'd have to react.
Most of the factions in Thedas think that Blood Magic is evil because it requires you to kill people to use its strongest spells and because you can use it to control people's minds.
This is deeply ingrained in their society and psyche and it is something that even the end of the world might not be able to overcome.
In the minds of most people Blood Magic= Daemons and since the Veil has been torn, then maybe a powerful Blood Mage did that, they did it before, when they polluted the Golden City , the Inquisitor is a power Blood Mage, maybe they torn the Veil and its trying to use it to take over Thedas.
With that line of thinking all of a sudden people don't want to be your allies, they want to kill you because they think it will solve the problem, you tell them that only you can repair the Veil, but why would they believe you, you're a Blood Mage. Cassandra tries to convince them that you are telling the truth but you could've mind controlled her to say that.
The Inquisitor becomes a convenient target for their fear of the unknown.
I will ask you then the same question I asked from phantomrachie (which he could not answer), Would all these factions let the world to be destroyed just because the only one person who can close veil tears uses blood magic?
I'd wait for a response next time before declaring that I can't answer something but I'm not sure you'd be satisfied with any answer that I gave