"Visually-wise", it should be possible to do what you need using Chameleon. I think this is your first option. Maybe in the process you will create "blue office style" chameleon skin useful for others.
If for some reason this is not possible, you can always do this: Make your copy of widget, *rename* it (to e.g. MyDropList) and apply your changes. Keep in separate package (MyCtrlLib).
Of course, we need to extend the library of widgets, that is in plans.