Vertical skips in paragraphs in L3

Consider the following:

TeX features some macros for fixed-length spacing.

smallskip Inserts a small space in vertical mode (between two paragraphs).

medskip Inserts a medium space in vertical mode (between two paragraphs).

bigskip Inserts a big space in vertical mode (between two paragraphs).

Are there any existing L3 code that redefines these vertical skips? If not, what would be the correct way to create similar commands with L3 syntax?

Note that the interface3.pdf defines skip_vertical:N which is equivalent to the TeX primitive vskip.