I have been successfully updating PSQL ( stored procedures/triggers/views ) for over 8 years, to thousands of sites and over the internet. As well as updating the applications that go with them.

The trick is to use the metadata to store the current version of the particular PSQL element.

eg.

UPDATE RDB$PROCEDURES
SET RDB$DESCRIPTION = 'version=2'
WHERE( RDB$PROCEDURE_NAME = 'PROC_MYPROC' )

run this after you update your stored procedure. You can reference what version is the stored procedure.

Have fun,

Robert.