But assuming it works in some form or other, it should remove most of the need to write a custom reader. Though there is still the issue of (for example) complex number syntax, etc.
It's in the standard (CLTL2). You can fix everything, because you can tell the reader to use your own functions on particulars characters, as an example this is a piece of code that lets you use Arc [... _ ...] syntax in Common Lisp: