You wrote "This plugin should work on the premise that anytime a widget is added to a sidebar, it’s viewable across the entire site where that sidebar loads. UI is added to the widget screen so that I can easily search or choose from the various template files that make up my theme to decide where the widget will be displayed." I say "Don´t" It defeats the entire purpose and fundamental idea of the system. Which is that we decide for ourselves where to add, and not to add anything. Better focus on proper Beta Testing than fancy new ideas. What we need is a rock-solid, 100 % reliable and fast product. The entire wordpress scene is going over the edge in creativity.