Now I can fully understand your indignation, especially since I am a member of a similar camp, and experience similar emotions and feelings with the occasional desire to put the game on hold and wait for patches. (Specifically, I want Minthara fixed and more content made for it, it's very sad to see it in its current form).
Yes precisely because Wyll and Karlach are willing to die for each other, it seems to me that something related to him would be logical, it is not necessary to kill him, but it is possible to link him with some very serious pact like Bhaal spawn.
And about the House of Hope and stealing the pact, if the pact is made with Mizora or Zariel, I don't think it can be broken or stolen so easily, because Raphael and Zariel have different levels of power.
Though considering how easily Dark Urge and Gortash stole the Crown from Mephistopheles, then....
