I think we should just leave the file manger thing alone personally. This is Windows Phone, not Android. I understand the pain as I came from Symbian and I understand some people 'need' a file manager, however I don't see this being implemented personally. There are a lot of security issues surrounding this and MS is big on security these days. If anything does come in, expect it to be severally limited compared to Android. Unless they change the whole concept of WP and open the APIs more, there will never be a file manager like you probably want it.
There are so many people on this forum from Android and Symbian going on about this issue. You should have looked into what WP could do prior to coming on board and it's time we let this go. My suggestion is this, give it to WP8.1, if the features you're dying for are not implemented it will be time for you to move on.
That's my take on this.