Michael,
I recommend you specify a CIP2 inspector with specific water tank surface preparation experience. CIP3 inspectors may not have as much "hands-on" experience as an abrasive blaster/coating applicator with an inspector certification. You should know that the interior space above the water line is the most frequent location of rust corrosion and coating failure due to inadequate surface cleaning and preparation. An inspector with intimate knowledge of tank construction and typical failure locations (dollar plates, rafter connections, support columns, locations inaccessible for surface preparation) will be able to identify problem areas likely to fail.
Brent Bergman