scripted looks like it might be a good choice: https://github.com/scripted-editor/scripted
Uses requirejs, so code should be fairly modular and easy to convert
Served from node.js
Nice, big application, looks like >2MB unminified javascript served
The only possible con about it is that I'm not sure it has much room for demoing async loading. If there was an app with lots of different windows, etc. it might be better... But maybe stuff like save/open dialogs and all could be loading async?