I would venture your "expert grader" really doesn't know what CGC is looking for. You say he missed 4 out of 7 books. That suggests to me that what he thinks is a 9.8 isn't in the eyes of CGC. I have learned what this means throught lots of experience.
I have submitted in excess of 1000 books to CGC.My average obtaining CGC grades of 9.8 is between 80-90%. Generally on pre-screens I can get close to the 90% range. I have never gotten 100%. I submitted 40 Amazing Spider-Man 539 (First Back in Black book) to CGC and got 39 9.8s. I still have the picture if you want to see it.
When I first starting submitting I was getting 9.4s and 9.6s occassionally. You really have to look a book over to insure it is a 9.8. Look at it at a sharp angle with a lot of light, if you see dents, pockmarks or spine stresses (more than 1-2 of 1/32 inch or less), even if they don't break color, you aren't going to get a 9.8. Same goes for corner dings, color rubs and other various dents.
As with all things that an art, not a science, grading is subjective, but the key is be consistent. CGC is very rarely inconsistent, but mostly they are on the mark. If you want 9.8 grades and the monetary benefits that follow you need to learn what make a CGC 9.8. You should seek out an expert grader that has a good track history with CGC. Feel free to contact me if you need some help. I can provide references such as the guy who produced only the SECOND GI Joe #21, the Silent Issue, in CGC 9.8.
Your suggestions about countrywide locations would only promote more inconsistency and further denigrate the name of CGC. You would start hearing stuff like..."Let's see these books in CGC Midwest, they don't mind corner dings as much as CGC East." Get my drift? GOOD LUCK!!