input nml:

spriteset(stationset1, "src/gfx/cc_grid.png") { tmpl_groundsprites(1, 1) }

spritegroup spritegroup1 { // alternatively: reference spriteset directly in spritelayout, and generate a spritegroup automatically using the same spriteset for all cases
  little: [ ];
  lots:   [ stationset1 ];
}

spriteset(stationset2, "src/gfx/cc_build.png") { tmpl_buildingsprites(1, 1) }
spriteset(stationset3, "src/gfx/cc_build.png") { tmpl_buildingsprites(1, 2) }
spriteset(stationset4, "src/gfx/cc_build.png") { tmpl_buildingsprites(1, 3) }

spritegroup spritegroup2 {
  little: [ stationset2 ];
  lots:   [ stationset3, stationset4 ];
}

spritelayout stationlayout2 {
 ground {
  sprite: spritegroup1(0, 0) // the second offset must be a compile-time constant, and is added to the first for Y direction. in this case use sprite 0 for both orientations
 }
 building {
  sprite: spritegroup2(0, 1) // use sprite 0 for X and 0+1 for Y
 }
}

switch (FEAT_STATION, SELF, switch3, [ ... ] {
  ...
  stationlayout2;
}

item(FEAT_STATION, station4) {
  property {
    ... nothing about layouts here ...
  }
  graphics {
    switch3;
  }
}


output grf:

action0:
  layout0: stationlayout2 using var10=0 for ground, var10=1 for building1
  layout1: stationlayout2 using var10=0 for ground, var10=1 for building1 and an additional 1 offset in the building for the Y orientation

action3
->  varactions according to switch3
    -> varaction(var0C)
         14: return layout0
         default:
           -> varaction(var10)
              0: return stationgroup1
              1: return stationgroup2