Just for the fun of it, I expanded a layout to fit your 6' X 16' space. One of the problems with that shape of a layout space is access. Unless you have all-around access (and it seems this space fits up against two or three walls), access beyond a 30" reach is a problem. So I came up with this idea that has an operating "well" in the center, with much better access. All of the turnouts are within a 30" reach, as are all but one of the buildings.
In the lower center are two lift-out 30" bridges. When these bridges are out, the "twice-around" route and the inner "loop-to-loop" routes are still operating. This arrangement solves the access for most of the layout in a convenient way. And the inner operating "well" is a fun way to have trains running around the operator - lots to see and experience.
This layout plan is done with Lionel Fastrack, but of course other track systems would work as well. The outer loop across the bridges is O-60 minimum diameter, so you can run O-54 locos and cars. The inner return loop-to-loop is O-48 minimum diameter. The approach tracks to the crossing in the middle are O-60.
The operating well is about 5' by 2.5' - deeper in the center, and a bit narrower toward the ends. This is a comfortable space for one person - or two kids would be possible, but two adults would be tight. Perhaps if two adults are seated with legs extending beneath the layout edge, it would be comfortable enough.