Hi Pete,
DCC has the stretch potential for constant, directional lighting and sound, items that become more important on a small layout. Most of my recollections of travelling the 'slam-door special' in SE London seem to involve the lights being on simply because the windows were so dirty, and then there's that noise they make when setting off. A Class 73 switching over from third rail to diesel would also be an interesting feature to hear.
That said, I've just junked DCC due to cost and the fact that some of my favourite locos are difficult (not impossible) to convert. If all your stock is going to be relatively long wheelbase, dead frog points wired to be permanently live in both directions really simplify the wiring - your fiddleyard could be a mare to wired up if using live frog. I ended up getting all sorts of weird and wonderful faults when I (wrongly) assumed I could just switch all my tracks to live with electrofrog points. I ended up having to install switched sections, which sort of defeats the object of DCC a bit...
Looking forward to seeing this one progress.
Al