AMP support for core components have been added already (see https://github.com/adobe/aem-core-wcm-components/pull/861), so I don't think that there is a need to build it on your own (unfortunately no version number is given for that PR, but should be part of the latest release already, please double-check).
To your question: The page rendering must hand down the "amp" selector to any component. Depending on how much you customized you have to do it either yourself (adapting the <cq:include> tag or its HTL pendant) or see that the product components do it. It would assume that with the adapted core component you are better off. Maybe they have taken a different approach though.