Maybe this will be obvious to someone with more medium to large farm experience than I have. I've got a custom Central Admin (.aspx) page that gets deployed to the \TEMPLATE\ADMIN directory. I also have a farm-scoped feature that puts a link to this custom page on the "Application Settings" page in Central Admin. The whole thing is deployed using a WSP.
Recently, we had a customer with a farm environment in which CA was hosted on an application server (they had 2 app servers, and 3 WFEs). The application server did not have the SharePoint Foundation Web Application Service running, per the Microsoft best practice. After deploying our WSP on one of the WFEs, the customer was running into a problem where the link to our custom CA page was not appearing. Upon further investigation, we discovered that the farm feature was also not installed, and the custom page had not been deployed on the CA server (the WFEs all looked fine).
The temporary solution was to activate the Web Application Service on the CA server and re-deploy the solution, after which the artifacts contained in the WSP were successfully deployed to the CA server and our page was accessible. This is only a stop-gap solution, and won't work for deployment to their production environment. My question is, why is this happening, and what should I be doing differently to allow my farm feature and custom page to be accessible from CA?