Windows Phone needs a more capable file picker

I am not talking about a full fledged file system. I think a productive OS needs a simple file picker which allows apps to share their files. The current state is that apps are only able to access pictures. I think there should be a more capable file picker. IE should be able to read PDF files stored in Adobe Reader and be able to upload them to web, Box app should be able to read documents from Office hub and so on.

I really miss this kind of functionality in Windows Phone. Sometimes I want to upload a simple file, say abc.txt, using IE but I cannot do this. When it allows a certain type of file to be downloaded from IE, Box or SkyDrive app (provided the file is supported by some installed app) why cannot it allow movement of files the opposite way?

What do you say?