You are assuming some sort of joined up organisation here. The customs side might not be an issue but the Special Branch one is.
Who would own such a website and keep it updated? There is no central special branch organisation.
AOPA have tried to get this done many times over the years and it is still one of the special projects I have on my list. Now if every pilot who intended to use such a system were an AOPA member maybe AOPA could be persuaded to do the work and run the website.