I think something got lost in translation somewhere in this thread. Either in the way I stated something or the way you read what I wrote. In any case my idea is identical.
Likely due to both. This was your latest suggestion:
I do however believe that implementing a file storage area which can be accessed by programs on the phone is still possible and I don't see how doing so would effect the security of the OS.
You specifically mentioned a storage area which can be
accessed by apps. If apps can access the common storage area, that gives them the ability to go on exploration trips across everything in it. That would even facilitate 3rd party file manager apps. That would definitely increase WP's attack surface.
Without any further input from you, that is still how I would I understand your suggestion, which is not identical to what Charles Roddie (and many before him) suggested, where apps have no technical means by which they can access, much less discover, anything outside local storage. Apps can only ask the user to "pass them a file from somewhere", by way of an OS provided component, and only for a temporary duration.
IMHO, you just never specified your idea to the degree Charles Roddie did, and I admit that amongst all the militant calls for a full blown file manager, I likely leaned towards interpreting ambiguities more along those lines then what you actually meant. Sorry.
Ironically, I actually wouldn't be satisfied with that solution. Why not? Because working with files in the common storage area wouldn't exactly be quick and easy. A PDF reader couldn't simply display the PDF files stored there (remember, no access), so we'd be required to open such files explicitly with the file chooser each time. It would likely also lead to everyone storing everything in the common storage area instead of in local storage, because only from there could we attach those files to e-mails, upload them to DropBox, or whatever. That somewhat defeats the purpose of local storage, and it is simply at odds with the concept of having app hubs be the entities that do file management for us.
IMHO, a common storage area's main purpose it to serve as a place to store files which either no app can work with (some random file off the internet), or multiple apps can work with (such as media files). It shouldn't become the default storage location for everything, which is what I think this suggestion, without further measures, would make it.
A few final comments:
Going by that PDF I found I don't see how malware would be an issue so long as people stick to using the MS Store.
Any security researcher will tell you that WP is the most secure mobile OS on the market. To a large degree that is due to the isolated storage and security level concepts mentioned in those documents. The limitations we're complaining about here are a result of those concepts. As long as the
security model stays the way it is, I don't see how malware could cause any significant damage either.
The whole reason for the clashing in this thread, is because almost all the suggestions made by the 'file manager' camp would have
required changes to the security model to function as intended.
I personally think, and this is pure opinion, that there should be some user responsibility when it comes to security.
I once agreed, but disagree now. That is how it should be, but experience has shown us that the average user simply isn't able to cope with that responsibility. Worse, at the end of the day, no matter how at fault a user may have been, it is the IT community that takes the blame. I know more than just a few MS employees who were frustrated with this. WP's though security model is a result of those experiences.