The blessing/curse of not getting started building the layout immediately is that there has been plenty of time to think and rethink the track plan etc!
Tomorrow I'm hoping to go and buy the wood for the baseboards etc. so once that's done it's done! But in the meantime I've decided to increase the width to 16", widening to 2' at the station end. This really is the maximum I can do realistically.
I've spent quite a bit of time thinking about the fiddle yard situation and I'm now veering towards the idea of having a very simple sector plate - simply a piece of 3'6" hardboard which moves freely directly on the baseboard. (The main advantage is that no space would be 'wasted' with pointwork - important given the limited space available - I want as much scenic area as possible.) Lining up the rails could be by sight, or else some sort of DIY system if necessary. Electrical current could be switched to the appropriate track via a switch. I think I could fit 4 tracks on the sector plate. This should be adequate, given that some man-handling of stock is going to be inevitable in any case.