Just one final update --
I now have a Chrome OS application that runs a local IDE, sends the sketch off for compiling on a remote server, and then takes the Intel Hex result and programs the Arduino locally. Takes just a few seconds for the round trip.
It does require Internet access for the Chrome App, but it works surprisingly well. Library support is very possible, but not written yet.
this new project might take a week or two to wrap up.
If you are interested, let me know, and I can set you up with a test account.