To get an interesting unique feature I recommend implementing generic dispatch a la CLOS or Dylan. That also makes your library writing a real joy, for example you can just write a plus function for each combo of types.

Check out Dylan, a high performance dynamic language that compiles to LLVM. Check out this example:

https://opendylan.org/documentation/intro-dylan/multiple-dis...

This is how to do it: https://en.wikipedia.org/wiki/C3_linearization

Gives the language powerful uniqueness feature that the 'mainstream' languages don't have.