Is there a good reason why the wp media upload button is not placed within the main edit toolbar, and can we put it there instead of floating above??
There is an action
In short: the current placement is better for plugins.
Moving the default button to the toolbar would probably break some core scripts that depend on that position in the DOM. Maybe you can move it around after
Just a proof of concept, not sure about the implications that @toscho signals, but at first it works as expected.
There's a glitch that makes a huge activation border when the upload button is clicked. Maybe another insertion point could solve it...
Note: the second jQuery command is not shown in the snapshot above. It will remove the text from the button. Replace with your own language.
Reference: jquery remove text partially