I would suggest expanding the number of certifying organizations besides the NRA. For example, I also have a Sig Sauer pistol instructor certification which is at a higher level than the NRA one, but does not qualify in Hawaii. I'd support allowing other organizations to certify instructors such as the HRA. However it's a big project to setup and maintain, so I doubt they would want to do it. One possibility is to have the community colleges offer a course for firearm instructors.
To clarify on the NRA membership, there are two separate things. One is basic NRA membership that anyone can pay an annual fee and be a member...you get the member card, magazine, hat, pin, and spam mail. This is not required to be a NRA instructor. The other is the instructor credentials where you have to take an instructor course and pay credentialing fees every two years to keep your instructor status valid. This one you have to maintain by paying renewal fees and teaching classes. If it lapses then you can't teach.