Access files are blocked content.

Please explain. I don't understand what you meant.

Opening a document  Library in an Access Database is probably not in the
Actions menu because the focus is on the documents, not the metadata.
With lists, the focus is on the metadata and the documents  are just
attachments so querying that content makes more sense. I don't know if
you can use a CustomAction Feature to add  the open  with Access option
but I doubt it.

I'll use Lists instead of Document Libraries where I want to open  with MS
Access.

Out of the box you can't store Access databases on SharePoint.