I'm confused, what emacs do you have in mind? For me, emacs is a lisp machine, hackable live, M-. all the way down, that kind of things, that's the whole point (again, subjective opinion, and I'm interested in yours).
What language do you have in mind?
If you're worried about performance, Common Lisp is a compiled language. It's about the best performing dynamic language there is, and not too far behind Zig, Rust and the likes.
Fair enough. FWIW, I know several lifelong Emacs users who never wrote or read a line of lisp.
But for those who do choose Emacs for its supreme hackability, I got a hunch that their profile is very similar to those who choose lisp for its unmatched meta-programming ; they're also very similar to the OG lispers who actually rejected M-expression, the normal, more mathy syntax with less parens, and embraced S-Expressions, precisely because (= code CST AST) is what gives lisp its simplicity and powers in the first place. It's not that we are stuck with parens anyway, the initial vision of lisp, with far fewer parens, has been implemented in Rhombus for example; and we don't even have to change language, 1 or 2 days of writing macros is all it takes to get your favorite lisp to understand many expressions without brackets, and even remove many brackets from existing code; for example, I'm using something close to
https://www.reddit.com/r/lisp/comments/18b6hf/comment/c8d8wt...
to write your example as (Too $ many $ god $ damn $ brackets), which btw, doesn't use any less brackets in an Algol language: Too(many(god(damn(brackets()))))
(but yeah, in many circumstances, we do use more).
This is why I have a hard time imagining an "emacs spawn" not written in lisp. Before even considering that many Emacs concepts are most easily transcribed in a lisp, who would be interested in writing and using it in the first place? (genuine question)
What language do you have in mind?
If you're worried about performance, Common Lisp is a compiled language. It's about the best performing dynamic language there is, and not too far behind Zig, Rust and the likes.