Step Copper PCB Circuit Boards With External layers has a Combination of the standard(4OZ) and Heavy /EXTREME(30oz) Copper
30OZ
If this heavy copper ,min trace width and space is 10OZ 25MIL 20OZ 50MIL 30OZ 80MIL
external layers has a combination of the standard and Heavy /EXTREME Copper.
See sample pic showing 2oz, 10oz, 20oz & 30oz
Yes,this can be done
Yes,but must enough big
Over 10OZ 1 layer and 2 layer more