If your layout is going to be on the floor, why couldn't you use an area rug or a decorative holiday blanket (points with wife?).
The area rug is usually round on the perimeter.
Hopefully you can find the correct 031, 036, 042, 054, and 072 curvatures on the corners.
Otherwise you could use a holiday decorative blanket.
A quilt has too many highs and lows.
You could fold/roll up the excess blanket on the curves and decorate the raised area as snow banks. These will make nice cushy places for the occasional hi speed engine to land during time trials.
If either blanket or rug was dedicated to the holiday train layout you could punch small holes in it to allow the wires to run under the blanket/rug and hide them from view.
