The user SAPCPIC was used in older releases (less than 4.0) for communication purposes, via RFC, between ABAP systems.
SAPCPIC was used mainly by program SAPXPG in order to return the delivery outputs of external programs again to R/3 system.
As of Release 4.0, another acknowledgement mechanism has taken its place.
Therefore, since then, there is no problem in changing its password through SU01 and even lock or delete the user if required, as this is considered obsolete in newest releases, although SAP do not recommend to delete users (so that history data can be kept for compliance & auditing purposes).
Hopefully this information will be helpful to you.