This foil is 0.003" thick CP4 titanium, and a waterjet will just mangle it. It gives a very rough, wavy, and grossly serrated edge. Others have tried that already with the same foil.
I've spoken to several companies about laser cutting this foil, and they all said that reflectivity should not be a significant problem. Laser cutting much more reflective foils is done routinely. But the cost is rather high and imobilization of the springy foil on the cutting table can be problematic (it wants to curl). For these reasons, it seems to me that chemical etching is a better way to go, but I would reconsider laser cutting if it were affordable and I had a contact who was willing to be creative about imobilizing the foil on the table.