Geo:
What you guys are doing is a smart move. The ICAO implementation and IS-BAO protocols make a point to state that small flight departments should tailor their program to fit their operation. Working with a "big box" plan may lead a small department to create administrative processes that are not needed.
What I've seen work best is for departments to work with a smaller auditor and get prepared for IS-BAO, then determine if the IS-BAO audit is something they want to do. That way they are prepared for an audit. Additionally, IS-BAO has been identified by ICAO as an acceptable means of compliance for the mandate. This means that if you get IS-BAO registered, that proves to ICAO (and their signatory states) that your department meats their SMS criteria.