Reusing or recycling quality management procedures does not count as integration, in my view. Suitability' does not mean certified, although that helps. It means effective, efficient, relevant, used, valued, etc. If you have any doubts, walk away from it. If you use a quality management system as a foundation for ISO 14001 without carefully checking for suitablity, any problems with the quality system will be replicated in the ISO 14001 system.
Care is required.