Ever since it was mentioned that Ragnar would meet and get beat up by Ghaz, I can't get the idea out of my head. It really would be a great way to get him Primarisified. In fact I have this whole story going in my head that I would love to see (even though I know it will not happen this way). I'd write up a fiction about it, but it breaks pretty much every rule of fanfiction and I'd probably get crucified if I actually wrote it and uploaded it somewhere...
Anyway, here's how it goes down in my head. Ragnar and Logan end up on a mission together and end up encountering Prime-ork Ghaz. He kicks the crap out of both of them but they hold him off while others escape or something else suitably heroic. Bonus points if the mission is mostly Primaris troops and Logan and Ragnar have a discussion about what to do with these new guys.
Anyway Logan and Ragnar get put under the Rubicon to save them. Logan starts talking like he's not going to make it (possibly because Njal foresaw that he's not) and talks a lot of Ragnar about leadership. Logan dies during the process and Ragnar gets Primarisified and appointed the new Great Wolf.
I think Ragnar getting his butt kicked would be a great way to tie in with his general character theme of "cocky kid learning to be wise" and make him ready to lead. And if we're going to take the whole "Rubicon is deadly" thing seriously, someone has to die. It's tricky because no one wants their favorite character dying on an operating table. But if you make sure they do something heroic to get them so injured they need the Rubicon, it could be done tastefully. And honestly I think Logan is one of the few big characters who is comfortable enough in his accomplishments to be okay with not dying in battle. If you framed it in a really good story themed around passing the torch, you could have someone die on the table and not have it feel cheap.