I would say that the “Export Attachment” buttons that shows up when you sendToChat() is good enough.
Out of the listed use cases it seems to me that the only one that really benefits from the proposal is “large file support”, Large files support [integrate with large file sending solutions and workarounds], which, IMO, should be solved differently from what’s proposed here.
I can see a more feasible and less confusing way to achieve the desired “ease of access to the exported files”: when exporting a file with “Export Attachment”, remember the file path, and then display the list of exported files somewhere in maybe a separate dialog / screen, behind the three-dot menu.