Heres something I worked out
this is a 4x6 Nscale track. Its got 8 industries (9 if you use the yard lead as another industry instead of a yard lead). You have a turntable with room for 5 engines, 3 runaround tracks, switchback sidings, and a long. non-oval mainline run (something like 3/4 of a scale mile). It's crowded, but there is still plenty of room for scenery, and of course, you don't have to include every siding.
the biggest weakness I see as drawn is that the yard lead shares the mainline, normally a big no-no, but this could be solved witha KATO or Peco crossover-switch at the second to last switch in the yard on the right, allowing the yard lead its own place. Atlas doesn't make a crossover-switch, and I used RTS to build this. There are a few S-curves, but all are formed from 19" radius curves, and are in sidings so should not cause most N-scale cars trouble.