I also think iOs should extend its current file management model to allow applications to DIRECTLY share their documents with other applications. The current model is good for the apps to easily protect their musics, books and any other documents with intellectual property rights from being copied. But it is a nightmare for the documents created by the iPad owners, no matter they are created on PC/MAC or by iPad apps. They became un-organized fragments isolated in many apps. Many of them have several duplicated copies.
This is caused by the way the iOs apps sharing documents with each other: If one app want to share its documents with another apps, the only way is to "Open With" the document using the other app. Then the document will be copied to the private folder of that app and being opened by it. It is ridiculas if you want to do some complex jobs.
E.g. if you have many documents of different types (e.g. video, books, pdfs, words, spreadsheets etc.). They are related to each other, so you want to have they being organized in one repository (either as a hierachical folder or as a list). Then you need to put them in one app (a master app), either
1. the app is able to read/write all the types of documents by itself, or
2. you have to use the "Open With" feature to open the documents in other apps(child apps) of your choice (e.g. Adobe Reader for pdf, numbers for spreadsheet etc.).
As we know, #1 is not possible. For #2, you will see how bad you will feel. Each time you open a document in the master app, the document will be copied to the child app. If you forgot to delete it, you will have one new copy each time it is opened!
You could ask why do you want to do such complex jobs using iphone or ipad. But I think it is not complex at all, many of our tasks have such requirements.
"iTunes U" developed by apple is one example. iTunes U has courses containing many sections. The sections could be of several document types: Audio, Videos, Books, PDF, and Web Links. iTunes U has built-in supports for Audio, Videos. For books, it opens with iBooks, for Links it opens with Safari. For PDF, it can open within iTunes U, and can also open with other pdf readers. The user experience for the audios and videos in iTuens U is elegant. The built-in player works very well and iTunes U provides add-value features for e-learning. And once you finished one section, you can get back to the course and move on to other sections.
But for books, web links, and documents, it is bad.
For web links, once you open it with Safari, you cannot back to iTunes U after you finished the section. You need to go "home", then open iTunes U. It is not elegant, although acceptable.
For documents, the built-in reader is not good (e.g. cannot search). But if you open with adobe reader or other readers, you will have the even worse problem than the Web Links. You cannot get back to continue in an elegant way. And you need to delete the copied document by yourself.
For books, it is also bad, and a little bit strange. iTunes U will move the books into iBooks the first time you open it in iBooks. It will keep the index in the iTunes, so that you can alwayse open the books from iTuens U and read it in iBooks. And it will not copy the documents each time you open a book. And iBooks can remember the current position of your reads to the books. And also, you can either delete the books from iTuens U or from iBooks and the status will be synchronized. It is good! But the problem is, the books are stored in iBooks, and you will see that the book shelf of iBooks will be full of the books of the iTunes U (there are many books in one iTunes U course). And also we'll have the problem that we cannot get back to iTunes U from iBooks in an elegant way. Why I say it is strange here? Because iTunes U and iBooks share the documents in a spetial way, I guess this is not available to third party apps. But this is not an ideal way. As we can see that the user experience of iTuens U is not good at all. This should be one of the reason so many iphones have their home button damaged.
I think apple just need very small change to their document management model: To allow apps(master apps) to Open their documents With other apps (child apps) in a shared way (in additional to the current way). In this way, the child apps can read and write the the document of the master apps DIRECTLY, and the document is not copied. When working in this mode, the child apps cannot access any other files and folders including their private files and folders. And child apps provide a "back" or "done" button to get back to the master apps.
I can see nothing harm to the security with this model. But it can solve all the file system problems iOs current have, and greatly improve the user experience (as simple as but more elegant than the current model, and as powerful as the PC/MAC/Andriod). We can imagine the improvement to the apps like iTunes U with this model, and we can expect much better third party file manager apps and tools apps.
As we'll see, pads and smart phones are being more and more powerful and not just enhanced iPod any more. If apple keeps the current file system model, we'll see more and more iPad and iPhone fans turn to the Andriod platform.