I come from the Flash world and have worked with it from version 5 on up to cs5, and have worked with all the versions of actionscript as well as the various ways that you can and cannot apply said script to objects and instances. The way that unity handles adding script to its game objects reminds me of 'the bad old days' of as1 and 2 where you were freely allowed to drag actions onto instances on the timeline. This was convenient but highly discouraged and (in my opinion rightly) forbidden in as3. It made finding code a nightmare on shared projects.
So my question is wheter you can totally avoid this style of coding in unity. Does the tool make it at all practical to never attatch script to game object instances in the editor?
You have to have at least one script on one object in your scene to add logic. The main reason is that Unity only sends messages to scripts in the scene. So you will never get an entry point otherwise such as `Start()` or `Update()`.
But you can create a single SceneManager that handles all the Game Logic in your scene. This would function as a global manager that could manage everything else. You can get references to everything else as well. It isn't a commonly used style in Unity, but you could use it without any problem.
I consider it quite convenient dragging scripts onto objects (OOP;-). Also I suggest to check the complete game tutorials to dive into Unity's concept. Finding scripts or something inside movieclips in millions of timelines was definitly a PIA in Flash, while it's not in Unity. Unity's concept is more streamlined it's not about encapsulating encapsulated encapsulations. If you have to work together with the creative department I would strongly suggest staying with "drag onto object method". With your AS3 background you should go for C# and Monodevelop.
You will find a lot of resources on the unifycommunity and the forums.