Provide hooks in APEX to allow developers to source help text via a custom PL/SQL function. Developers could then add their own code to get the help text from a local DB table or even a centralized source via a REST call.
I have worked with several customers who want to maintain their own database of help text. This allows end users, instead of developers, to maintain help and additional information. My solution offers customers ultimate flexibility in where to source help from.
Preferred Solution (Optional)
Wherever you can add help text in APEX currently, include an attribute in the APEX builder to allow you to enter a custom PL/SQL function name. If help is invoked for the page/item, then the custom PL/SQL function should be invoked by APEX, and whatever text is returned should be displayed in the page/item/column/in-line help text. The function should include the following parameters, which should be defaulted: app_id, app_page_id, item_id, type (page,page_item,report_column, etc.).