If Emacs did take key binding customization seriously, it would have
> provided a whole bunch of*declarative* methods for specifying key
> bindings, along with rules for how they override each other or not
> override, as the need may be.
I understand what you want. But, I'm not 100% sure what a good solution
would look like, and I'm even less clear on how we could get to such
a solution starting from Emacs's current system.
The main problem is not whether the method is declarative or not, but
rather the problem is to make intentions clear.
The issue with "intentions" is typically along the lines of "do you want
to bind `foo' to C-x C-x or do you want to bind it to the C-x key within
the main prefix keymap, or do you want to bind it to the repetition of
the key-sequence to which this main keymap is bound, or maybe only to
the repetition of just the last key in this key-sequence, or maybe to
the repetition of C-"the key above my "alt" key, or maybe you want to
bind it to whichever key `foobar' is bound in such-and-such-mode, ..."