CALL is suitable for loading libraries at run time.
The INCLUDE that has been proposed and may make it into a future release is not best suited to loading libraries for most applications.
The proposed INCLUDE is designed to in-line code when a script is tokenised, similar to linking static libraries into a single executable in languages like 'C'.
The benefit is that (when tokenised) the libraries are all included in the script file, so you have single tokenised script which you can distribute.
The bad news is that every script which has an INCLUDE is bloated by the copy of the libraries, and when you change the library you need to re-tokenise every script which uses it to get in new version included.
If you simply want a centralised store of common routines that you want to include in your scripts, CALL will do the job nicely and is already available.