We don't have any of those. #'+ is part of the core and can't be extended. There's also no facility for type propagation in library form.

To extend #'+, equality functions and much more, see https://github.com/alex-gutev/generic-cl/. See also https://github.com/pnathan/generic-comparability

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.