You might be interested in my lang/environment "mica" which attacks this same dimension of problems from a relational/datalog angle and then makes object/prototype identity hopefully emergent out of that: https://github.com/timbran-project/mica -- relational dispatch feels like a broadening of multiple dispatch.
I feel like I may have ended up at a similar place as Korz without realizing it. I will need to dig into this paper.
Speaking also of multiple dispatch and prototypes, there's also this paper from an old acquaintance: https://www.cs.cmu.edu/~aldrich/courses/819/salzman-pmd.pdf which I used to find interesting (and built my first version of "mica" back then around the idea).