I agree that there is a GAP in this industry and maybe an association could be the way forward although dealers are very very skeptical, myself included, about anything relating to this industry. I have found some of the responses vague, the information about the actual services / products available hidden but I did find a welcome video which shows to me that the IMDA doesn't offer anything useful for my business.
I agree the power is in the numbers. A simple and I do mean simple association with no gimmicks, no promises of `we can offer this and that` but just a simple association to simply say enough is enough and it's time dealers had a voice. I think you've made something which should be so simple, into something more complicated and skeptical.
If you're doing something like an association then you shouldn't need to have a membership system for payment. You need voices to be heard but you're putting a hand over the voices you want to speak.
You should get the numbers first then start with offers. Many dealers have their own lawyers in place, they have suppliers, good insurers, good accountants, etc. Once you have the numbers then you can say ok, if you want to benefit from XYZ then it's XYZ per annum to those who want it. Most just want to be heard.
Just my 2 cents, wish you all the best with it.