Is it possible to have a persistent ScriptUI panel with buttons that hovers over the artboard and while in that state have the ability to click "zoom in/out" and the equivalent of "up/down/left/right arrows" to scroll about the document. The "Insert Page Numbers" script is a good example in that you could only click on the panel itself while active ... therefore a scriptable execution of "up/down/right/left" scroll sctions would do the trick.