Personally I'd love it if BLMA or NJI did harp style wigwags. NJI has more "western" style, but I'm used to seeing the different style here in the midwest. Also, what I always thought might be cool is a depot work a working clocktower. I know you could probably bash one together using "cheap" watches, but... Better variety of modern vehicles and buildings maybe...lots of the cars I see at my LHS are older styles.
I agree with so many of the thoughts that have already been posted... MP15AC SDP40 More SD40-2s SDL39 More detail parts A new Wilson Grain trailer would be nice As well as some modern precast (tip-up) buildings.
I am just going to reiterate the comments from another thread regarding the desire for an RS-32/RS-36 in N Scale. It would be really ideal for kit bashing Canadian prototype RS18s.