I like to request a new field in SEC$USERS that reflects whether a user has the RDB$ADMIN role in the security database (as a result of CREATE USER GRANT ADMIN ROLE).
Suggested names for this new field: SEC$ADMIN_ROLE or SEC$ADMIN, value 0/1 or boolean.
This is the only user info missing now in sec$users, that can be obtained by the service manager (isc_action_svc_display_user_adm).
Note: special consideration is needed for user SYSDBA because this user is of course an administrator, but has not the RDB$ADMIN role been assigned in the security database. I suggest to assign 0 for this user to the new field because this is also the case for fbsvcmgr action_display_user_adm.