I think its important only add those things after the language can run the same sorts of programs C can currently.

For the future, some of my ideas include:

a form of combined data types that require a type-switch to disambiguate (and is checked by the compiler), like algebraic data types. (essentially sugar over tagged unions)

It may also have a form of defer blocks similar to Go defer statements. (sugar over the C idiom goto cleanup;)

A final thing I considered was a built in reference counted pointer type. Just to partially alleviate memory management, but without resorting to a garbage collected run time.