I can't comment of all of the options you may have, but I know that most plasma machines use slats like you're suggesting. I find that after the slats are used for a bit, you start to get sort of a bed of nails kind of support anyway. The slats are the only simple alternative I found that makes replacement easy and cheap. You can also flip and turn them to extend their use. The only issue at times is buildup on the sides and it may be easier to replace than take time trying to clean off the crud. I made 3 steel crossbars from angle that have the slots cut in them for the slats. A small piece of angle is welded perpendicular on each end of the three cross bars so that they "hang" across the machines bed/frame and the slats are simply dropped in place/installed. That way I can easily adjust the bars for extra support if needed or remove the entire setup and use a standard bed for wood work. It's fairlly straightforward but works well for me. Have fun!