Certification is tough because the nature of it implies that you have a knowledge of standards and certification is a simply a testament that you can pass a test demonstrating technical and diagnostic competency applying those standards to solve problems.
The problem that precedes certification is an agreement of what those standards are, and deployment of training materials to educate folks on those standards.
For iPhones at least, no such standards exist. Without ratification of a set of standards from a wider community of folks operating in the field, there will never be any buy in for any certification across the industry.
This is what I learned from working on a phone certification from ifixit.
So the first step is a gathering of people committed to developing those standards for a community since those standards are either not issued from the manufacturer or the ones that are--in the case of iPhones at least--are laughable.
My suggestion is to pull together people that have experience running successful repair businesses and challenge them to battle it out to develop some basic standards for diagnosis and repair of common problems.
For example--what is the best way to change iPad broken glass? Right now, you'd find a range of answers to this question with significant disagreement on adhesives and methodology.
If we could get agreement on even just a few standards we could begin to develop a set of tools, parts, and instructions that form the basis of a standard that could be tested and a certification to those standards created.
