> However, Yao will not have inheritance; instead, it will be more like Go: composition over inheritance. And interfaces. So I could be wrong, but without inheritance, I'm not sure the entire complexity of the CLOS is needed. Do correct me, though.

I'm sadly not very well versed with this alternative to OOP. But something tells me that a more "basic" and less dynamic scheme like that is probably best for performance reasons, since you'd either need a Julia-like JIT or a granular "dynamism knob" like https://github.com/marcoheisig/fast-generic-functions to truly amortize the cost of CLOS-like dispatch and polymorphism; though magic can be done, as the "Fast generic dispatch for Common Lisp" paper shows.

> if those are just for giving info to macros, Yao already has that

Huh! If this includes types deduced by compiler inference and not just user declarations (since Yao seems gradually typed, to my eyes), that'd be pretty impressive.

Hope you'll be able to keep your spirits high, this is a lifetime's work you seem to be looking forward to ;)