TL;DR in pink...
@OP I would say this is not so much a Sublime fault as a user error (no offense, just being frank). I thought about this for a few moments after reading it (your post that is), and considered if it were such that one couldn't open files outside the current dir: that's just about every IDE worth naming; Aptana, Komodo, Eclipse etc. Okay maybe not every IDE - that's an exaggeration for emphasis, but I think you get me?
There are IDE's that require that you assign a dedicated project folder, and won't allow opening non-project files. A lot, perhaps most of them do: Aptana, Eclipse etc. There's nothing wrong with that (by the way, isn't Git, Hg, and in fact most file systems designed to work within, but not outside the current dir and subdirs (think C:/System). Even symlinks do that, we as users know that they are symlinks, but the stupid computer is sort of "fooled" into believing they are in the subdirectory.
But I digress.
I like that Sublime is drag and drop, plug and play and if I have to leave or the computer crashes, I close the window... badaboom it reopens instantly all my files. I do this: have a 'general' workspace project that is basically always open, and I actually don't type IN-BROWSER anymore because if it crashes or reloads the page... my text is gone (on Chrome. I know there is Lazarus and it was brilliant on Firefox, but I find it to be a cache hog on Chrome). This post was written in ST2. I don't use Word anymore either, if I need it, I type in ST2 then copypaste to Word.
ST2 is my to-do list.
ST2 saved my life. I am grateful. Thank you, ST2!
In my opinion, as a result of my own findings after much trial and error (more error than trial), the most important part of the project consists of two stages:
1. Literally plotting things out with pen and paper, then
2. Compiling, as accurately and conclusively as possible the elements, files, media, code, and so on at a dedicated location.
I'm not pointing fingers and saying that you can't really blame the app for this, but you can't really blame the app for this.