I really wish someone would put together a new standardization of Common Lisp. The language could be much better with a few minor tweaks: for example, (function +) should be a generic function --- that it is isn't is a silly oversight. Compiler macros should have access to type inference information so that they can do a better job: right now, they're purely syntactic and give up lots of optimization potential as a result.
You can shadow + and use your own implementation in your code, falling back to cl:+ when appropriate. Changing the existing language may be difficult, but building a modified language on top of it is possible: see Shen.
