How to extend ui from API

My question is about concept (I need some recommendation how to implement it right). I've use MVC pattern when I build the UI,currently this UI serve two plug-in since the UI they should use are identical. so both plugin call to this UI and this is working fine.Now there is third(and four :)) plugins which should use some of the UI control and logic so instead of build new UI for this plugin's I want to provide some mechanism to enable to the user to decide which control he want to draw in the screen. so currently I need to break the view to sections but my question is what it the best way to do that ? (from design and concept aspects)

The view is build from 6 controls that all the plugin must by default use two from them and the rest are optional . for example new plugin can use the mandatory two and provide in addition two more control.