I would like to start by changing the name from 'Mechanic' to 'Technician'.
It would be great to have an organization to establish standards. An organization that gains the respect of table manufacturers, and uses input for table design.
As a benefit, members can gain some sort of "Certification" for performing various types of work. As we all know, there is a range of skillsets in this business. Some are great at leveling a table, some great at installing cloth, some better on barboxes, some better on home tables, etc, etc.. To be proficient in all facets of the job, merits a "Master" status. Of course, this includes having an in-depth knowledge of tables, and the skillset to perform any required task.
As an established organization, the benefits should include suppliers: a list of preferred suppliers, with potential for discounts.
I believe that membership should have strict requirements. Even more so, the Certification requirements should be even more strict. Being a member is one thing. Calling yourself 'Certified' is something completely different. Extensive vetting is required.