creating languages in the pg_catalog schema?

Just wondering if there are any downsides to creating a procedural
language in the pg_catalog schema instead of some other default schema.
I want the language to be available forever, regardless of schema drops
etc., to every user of the database, in every schema. And since I have
the impression that PostgreSQL (secretly) adds the pg_catalog schema to
the searchpath, it appears to be the obvious place to create the language.

Using the code below it appears to work, but are there any downsides?

CREATE FUNCTION pg_catalog.plpgsql_call_handler () RETURNS OPAQUE AS
     '$libdir/plpgsql' LANGUAGE C;
CREATE TRUSTED PROCEDURAL LANGUAGE plpgsql
     HANDLER pg_catalog.plpgsql_call_handler;


Best wishes,

Jochem