(Sorry, haven't read past page one. Apologies if this has already been addressed.)
One can easily keep Bull loyal to the Inquisitor without metagaming. For instance, I believe getting a Qunari to abandon the Qun is a major victory for the other races of Thedas and a minor blow against the Qun (but every little bit helps). We can play characters who believe this, and as a result, will stress the value of friendship over mindlessness, thus giving the Qunari one fewer drone to use and abuse.
Even if you dislike Bull (like I do; no offense, Bull-lovers
), you can use this as the reason to keep him as a "friend." Otherwise, if you love the Chargers (and want to recruit them) but loathe Bull entirely, you can just avoid doing his personal quest altogether to keep the Chargers alive, but kill Bull in the DLC! Either way, you'd avoid a phony alliance in the end. Not that our characters who chose this would know it turned out to be phony.
On that note, our characters know all about what happened in Kirkwall. It's not metagaming to be skeptical of the Qunari and their supposed alliance. Especially when their Ben-Hassrath agent tells you upon meeting him that he spies for the Qunari. It's also not metagaming to value the lives of the Chargers (if your Inquisitor admires them) over brainwashed oxmen they've never met before (individuals b4 drones). Keep in mind that the Qun readily throws away lives for the littlest reasons, as if they mean nothing. Letting a dreadnought sink is likely not a serious loss to them, though I'm sure they'll use any excuse to invade the south.
Just my take on it.
Still wish there was an option to recruit Bull and the Chargers as agents instead of automatically having Bull in our Inner Circle. I love the Chargers, just not Bull himself.