This is my first post, so please go easy on me as this is a bit of a disjointed theory.
Speaking with a friend while reading through Oathbringer, we were talking about what might be the other 2 Bondsmith Spren. I think everyone assumes the Nighwatcher is the 2nd. The "one that slumbers", I don't think is a crazy stretch to assume is possibly a spren somewhat entangled with Uruthiru.
If honor and cultivation are responsible for half of the surges on the Surgebinding chart, how is the 3rd Bondsmith spren connected to the magic system? My thought is that the 3rd spren, Uruthiru's spren, is connected to the ancient fabrials. In a similar way that Shardblades and Shardplate are bastardizations of what was originally wielded by Surgebinders, I believe modern fabrials apply a misunderstanding of the original fabrials.
Where Shardblades are dead spren, the fabrials trap or enslave spren to perform a function.
Bringing this all together, I believe Navani starts to make some discoveries when it comes to fabrials, and eventually bonds with the spren of Uruthiru. She will come to be horrified about how modern fabrials have enslaved spren.
I'm not a big fan of the possibility of all the Kholins becoming surgebinders, but this just seems to straight forward.