Hi Ifran,
Recommend that you use PCo amd MII to integrate to ECC. MII has JCO and BAPI connectors for ECC as well as the capablilty to implement Listeners to receive IDOC from ECC. MII has additonal capabilities such as the Plant Information Catalog that will be very beneficial in defining historian data and providing business context around it.
PCo has a native OSP PI connector as well as MII connectors that can execute MII transactions directly; the transactions can then execute JCO and BAPI to ECC.
PCo can connect to Honeywell PHD using the PCo OPC HDA connector. (The Honeywell historian OPC server will need to be installed and activated, preferably on the PCo server.) PCo also has connectors for TCP Socket, OPC DA, OPC UA, OPC AE, ODBC, OLEDB, FileMonitor, and additional native historian connectors (Aspentech IP21, GE Proficy, CiTectSCADA).
Regards, Steve