I think you can integrate all you want. The question most people ask is how auditing (for certification purposes) days estimation is done when an organization has an integrated management system and is applying for dual certification, e.g., ISO/TS 16949 and ISO 14001.
The FAQ at the IATF website states:
This clarification is now Rules 3rd FAQ #1.
[FONT=Times New Roman,Times New Roman]Previously FAQ 7 [/FONT]
[FONT=Times New Roman,Times New Roman]If an IATF contracted certification body conducts one audit to satisfy management system standards in addition to ISO/TS16949:2002 the IATF Rules for Achieving IATF Recognition for ISO/TS16949:2002 shall be observed. [/FONT]