Right now 508 decisions are made with almost no transparency. This leads to disparities among agencies, and insufficient information about accessibility for other decisionmakers -- basically everyone who buys or uses ICT. (Remember, 508 is supposed to benefit the entire ICT market.) For example, why are VPATs treated as private communications between an agency and a vendor?
All information about ICT accessibility should be public, and published in a manner most likely to see it shared usefully across the entire user base. Mainstream and AT vendors, people with disabilities, ICT implementation managers, advocacy organizations, researchers -- all have a lot of expertise to offer. Sharing our testing results and methodologies, AT compatibility notes, tips and tricks, etc. will immediately improve accessibility, and build long-term resources.
Ironically, it's been non-federal folks, especially higher ed, who've done a great job already in this direction. But the information is still too tightly held.