Interesting. I can see what you mean. I remember though a conversation about the re-educators that Bull and the Inquisitor had. About changing how someone thinks. Bull went to them before. Predicting someones actions, or helping guide them through social engineering isn't unheard of. I'm still more towards them trying to test Bull, or force him to choose, but I see what you are saying. Though, it wasn't uncommon for groups or governments to sacrifice troops or spies to ensure the loyalty of a higher ranked officer. It happened in Japan, Persia, and many ancient states. Still does in some cases. After all, we only have the word of the Qunari agents as to the conditions of this mission. I doubt even Gatt knows everything.
Also, I admit that this can be chalked up to a writing flub.
True. Assisting the Qunari does give insight, and left alone, they may become a dangerous unknown quantity. That is a very fair point. I don't know if they will fail without the Inquisition helping them...perhaps in that instance, but as nothing further is revealed, its unknown if the Venatori get as far as they do without. Some of it might have been caught by Leliana's people and neutralized before it ever got to the War Table. Unknown. There REALLY should have been something further, consequences and such for picking a side. If THAT had been the case, it would have added depth to your choice, making it harder to just say 'Chargers Forever', and be done.
As to the allies, I'm sure they know, or WILL know. Word travels, and soldiers gossip. The Chargers don't come back, some one WILL talk. They have spies too. Your Orlesian and Free Marcher allies WILL hear of it...it's just a matter of when. Orlais will be shrewd, MIGHT accept it, but the Free Marches would consider it a slight.
AGAIN, there should have been a bigger impact about your choices. The more I think of it, the more it saddens me that this wasn't thought out more. This could have been a big thing. Had a big impact upon the game. Darn it... 