轻量级IDE应该使用什么设计模式?

I'm writing a lightweight IDE. I chose Ruby+Gtk2 for the task. I already have a minimal prototype for it, but right now, most of the code is inside my window class. I'll soon start working on the "real deal", but I would like to know what design patterns should I make use of. I'm planning for plugin support too, so that the app will be extensible. Any ideas are welcome, but please discuss your option a bit. I'm writing a lightweight IDE. I chose Ruby+Gtk