Kerf, I have been thinking about doing something similar to your idea. I don't think I will be going with a deralleur just yet, as I think that I will mostly use the cruise unless I want to do some mountain riding. For now, i don't mind backing up and moving the chain manually.
I do have some questions about your tensioner though. It looks like you are using some kind of neoprene skateboard wheel sort of thing for your tensioner rollers. Why not put sprockets there? Also, what is the tensioner pivoting on? Does the pivot use a bearing of some sort? I have been using a GEBE system and the tensioner really does not actuate all that well because it is rotating directly on the bolt threads...
I looked through the thread, but I apologize if you already answered these questions. I also have not yet ordered my Staton kit, so if you have any pointers, that would be great!