It does also encourage you to create mini-languages, but our approach was usually a large amount of modular Racket-y code with many fairly thin layers of syntax transformation used in each mini-language case. In that sense the problem of mutually incompatible languages didn't really arise (in fact, separate mini-languages coincided with separate usage areas quite well).
Performance was an issue, and we generally needed to use the precompilation feature of Racket to be successful. The issue we ran into is that Racket's precompilation system produces fairly fragile and coupled binary files -- and is generally difficult to separate cleanly from the execution environment.
ANSI Common Lisp's one and only 1994 standard is over 1000 pages long. The Scheme reports are a lot smaller, though growing. I think still under 100 pages.
I developed a Lisp dialect that has a dense reference manual that is over 530 pages long with no table of contents or index.
Clojure and Common Lisp are larger languages and don't really suffer this problem.
Did you have any problems with development speed or performance in production or was that fine?