And you can create the abstractions necessary to work with such a data structure and add them straight to the regular grammar of the language. Lisp also has al

And you can create the abstractions necessary to work with such a data structure and add them straight to the regular grammar of the language. Lisp also has all of the other low-level primitives we're used to when working closer to the machine. Structs, indexed arrays, hashes, etc. If efficiency is a concern, just pick an implementation that compiles to machine code. SBCL is pretty good for this depending on your target platform. Replacing conses seems like a waste of time.