Brief the Emperor seems to be holding a lead. I suppose we have enough results to brief him. There's a bunch of topics we can broach and it does look promising. Being able to tell him that we have working tributariy prototypes would be nice, but I do have to note that we haven't exactly erected any yet. We'd literally be telling him "we have a workable ritual for setting up tributaries", and if he asks us if we made one we'd have to say "No, but the theory is solid".
Thankfully we have a ton of other things we could mention, such as improved trade relations, greater knowledge of the Eonir's inner politics, progress on intersectional politics, and most importantly of all, the Vorbergland thing. Literally everything else is an appetizer compared to Athel Yenlui. Knowing the source of his province's fertility and knowing that it's the only recourse the Empire has in case Marienburg falls is incredibly important, and I imagine he will immediately mobilise resources to secure the location. I imagine whoever the local noble is might take issues with that, so maybe he'll be more diplomatic about it.