It's a good idea, but not so necessary. ST2 orienter for keyboard-driven work, i mean w/o mouse, for this case - better to keep sidebar open.

EXT JS? It's just a Javascript, or you want autocomplete for it? Anyway, you can write it yourself.
CFML? See at TM bundles. If it available - pick it up and make extension for ST2.

At first, ST2 _dont support_ TM-bundles. It just uses similar to it language files, but anyway you need to review this files and correct some thing. Also, TM uses compressed files using Mac OS proprietary tech, which makes this pointlessly.
But i understand what you want. You need to recreate idea with just text like: "Bundles manager".

As i know, ST2 uses different, selfwritten UI toolkit or, at least, UI widgets. For UI api, need to build UI elements, but it's harder than just add some funcs.
As i think, this idead will be moved on ST3 or ST4 release.

Oh. Can you explain me, is it really comfortably? So, i dont think so.
It isn't helpful for "easy selecting", also "with coupled with custon keys".
You can use easier way - shift+arrows. It's easier, than pressing c-spc with selecting using arrows. It's really faster.
So, i want to say just one thing: dont keep bad practise thing like this one. Emacs, like some of vim, key-bindigs and some features are bad things, really bad.
I love KillRing, but i hate "Windows Manager" feature and key-bindings.

Maybe it easier to use it in auto-completer or snippets. 4 keybingings for such small functions - really too... hard.

In the nutshell - no. Imagine this case: you wrote some app, some in vim, some in ST2. But! Files, written in vim, are folded in ST2 and it won't be added in the tree. What happens if you'll try to build project via ST2? It could give a rise for bunch of bugs.

This is a build system improvement, not a ST2. I think, better to move this functionality into separated plugin(i believe Jon read this message +_+) and give it to community.
But now, best solution - add arguments using "Build with arguments". And nothing need to add in ST2.

Plugins can define keybindings commands, which can be associated with keybindings by user or plugin itself. Isn't?

It seems it's a bug on OS X. It's light on my Linux Ubuntu and Dark GTK theme.