Yo, this may sound pretty far-fetched and I'm really stretching here, but here we go:
I just watched one of BellularGaming's videos which was about the end of our artifacts, and one of the points he made was that when we use our artifacts to contain the corruption of Sargeras' blade, we are not destroying that power, we are merely containing it. There are a couple of artifacts with actual beings inside of them, namely Aluneth and Xal'atath. The latter of course being much more relevant, and now it is partially empowered by the most powerful being in existence.
This is where I'm stretching: it does sound a very reasonable request to draw the power spilling out of the blade into our own, but is it possible that Magni only wanted this to empower Xal'atath, with the added bonus of nullifying the most powerful weapons on Azeroth. At this point we have taken everything Magni has said as gospel by virtue of him being the 'Speaker' of our own Titan, but it isn't perhaps too far flung to imagine an Old God influenced attempt to get the mortal races to stop at nothing to stop the Legion, as the Old Gods are I'm sure well aware of what Sargeras intends/intended to do with Azeroth. How do we know he's actually speaking for Azeroth? What if the ritual that turned him into diamond was an Old God intervention? (I admit to not knowing much lore-wise about his transformation).
Maybe too wild, but I found it certainly interesting. Do you think it's possible?